50001456J.pdf

16-Bit Language Tools Libraries
Reference Manual
 2004-2014 Microchip Technology Inc.
DS50001456J
Note the following details of the code protection feature on Microchip devices:
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Microchip products meet the specification contained in their particular Microchip Data Sheet.
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Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the
intended manner and under normal conditions.
•
There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our
knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data
Sheets. Most likely, the person doing so is engaged in theft of intellectual property.
•
Microchip is willing to work with the customer who is concerned about the integrity of their code.
•
Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not
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Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our
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Information contained in this publication regarding device
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and may be superseded by updates. It is your responsibility to
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Trademarks
The Microchip name and logo, the Microchip logo, dsPIC,
FlashFlex, flexPWR, JukeBlox, KEELOQ, KEELOQ logo, Kleer,
LANCheck, MediaLB, MOST, MOST logo, MPLAB,
OptoLyzer, PIC, PICSTART, PIC32 logo, RightTouch, SpyNIC,
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trademarks of Microchip Technology Incorporated in the
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The Embedded Control Solutions Company and mTouch are
registered trademarks of Microchip Technology Incorporated
in the U.S.A.
Analog-for-the-Digital Age, BodyCom, chipKIT, chipKIT logo,
CodeGuard, dsPICDEM, dsPICDEM.net, ECAN, In-Circuit
Serial Programming, ICSP, Inter-Chip Connectivity, KleerNet,
KleerNet logo, MiWi, MPASM, MPF, MPLAB Certified logo,
MPLIB, MPLINK, MultiTRAK, NetDetach, Omniscient Code
Generation, PICDEM, PICDEM.net, PICkit, PICtail,
RightTouch logo, REAL ICE, SQI, Serial Quad I/O, Total
Endurance, TSHARC, USBCheck, VariSense, ViewSpan,
WiperLock, Wireless DNA, and ZENA are trademarks of
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SQTP is a service mark of Microchip Technology Incorporated
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Silicon Storage Technology is a registered trademark of
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GestIC is a registered trademarks of Microchip Technology
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All other trademarks mentioned herein are property of their
respective companies.
© 2004-2014, Microchip Technology Incorporated, Printed in
the U.S.A., All Rights Reserved.
ISBN: 978-1-63276-906-0
QUALITY MANAGEMENT SYSTEM
CERTIFIED BY DNV
== ISO/TS 16949 ==
DS50001456J-page 2
Microchip received ISO/TS-16949:2009 certification for its worldwide
headquarters, design and wafer fabrication facilities in Chandler and
Tempe, Arizona; Gresham, Oregon and design centers in California
and India. The Company’s quality system processes and procedures
are for its PIC® MCUs and dsPIC® DSCs, KEELOQ® code hopping
devices, Serial EEPROMs, microperipherals, nonvolatile memory and
analog products. In addition, Microchip’s quality system for the design
and manufacture of development systems is ISO 9001:2000 certified.
 2004-2014 Microchip Technology Inc.
16-BIT LANGUAGE TOOLS
LIBRARIES
Table of Contents
Preface ........................................................................................................................... 5
Chapter 1. Library Overview
1.1 Introduction ................................................................................................... 11
1.2 OMF-Specific Libraries/Start-up Modules .................................................... 12
1.3 Start-up Code ............................................................................................... 12
1.4 DSP Library .................................................................................................. 12
1.5 16-Bit Peripheral Libraries ............................................................................ 12
1.6 Standard C Libraries with Math and Support Functions ............................... 13
1.7 Fixed-Point Math Functions .......................................................................... 13
1.8 Compiler Built-in Functions .......................................................................... 13
Chapter 2. Standard C Libraries
2.1 Introduction ................................................................................................... 15
2.2 Using the Standard C Libraries .................................................................... 16
2.3 <assert.h> diagnostics ................................................................................. 17
2.4 <ctype.h> character handling ....................................................................... 18
2.5 <errno.h> errors ........................................................................................... 27
2.6 <float.h> floating-point characteristics .......................................................... 28
2.7 <limits.h> implementation-defined limits ...................................................... 33
2.8 <locale.h> localization .................................................................................. 35
2.9 <setjmp.h> non-local jumps ......................................................................... 36
2.10 <signal.h> signal handling .......................................................................... 37
2.11 <stdarg.h> variable argument lists ............................................................. 43
2.12 <stddef.h> common definitions .................................................................. 45
2.13 <stdio.h> input and output .......................................................................... 47
2.14 <stdlib.h> utility functions ........................................................................... 97
2.15 <string.h> string functions ........................................................................ 122
2.16 <time.h> date and time functions ............................................................. 145
Chapter 3. Standard C Libraries - Math Functions
3.1 Introduction ................................................................................................. 153
3.2 Using the Standard C Libraries .................................................................. 153
3.3 <math.h> mathematical functions .............................................................. 155
Chapter 4. Standard C Libraries - Support Functions
4.1 Introduction ................................................................................................. 197
4.2 Using the Support Functions ...................................................................... 198
4.3 Standard C Library Helper Functions ......................................................... 199
4.4 Standard C Library Functions That Require Modification ........................... 204
4.5 Functions/Constants to Support A Simulated UART .................................. 205
 2004-2014 Microchip Technology Inc.
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16-Bit Language Tools Libraries
4.6 Functions for Erasing and Writing EEDATA Memory ................................. 208
4.7 Functions for Erasing and Writing Flash Memory ...................................... 211
4.8 Functions for Specialized Copying and Initialization .................................. 216
Chapter 5. Fixed-Point Math Functions
5.1 Introduction ................................................................................................. 219
5.2 Overview of Fixed-Point Data Formats ...................................................... 220
5.3 Using the Fixed-Point Libraries .................................................................. 223
5.4 <libq.h> mathematical functions ................................................................. 225
Appendix A. ASCII Character Set .............................................................................245
Index ...........................................................................................................................252
Worldwide Sales and Service ...................................................................................266
DS50001456J-page 4
 2004-2014 Microchip Technology Inc.
16-BIT LANGUAGE TOOLS
LIBRARIES
Preface
NOTICE TO CUSTOMERS
All documentation becomes dated, and this manual is no exception. Microchip tools and
documentation are constantly evolving to meet customer needs, so some actual dialogs
and/or tool descriptions may differ from those in this document. Please refer to our web site
(www.microchip.com) to obtain the latest documentation available.
Documents are identified with a “DS” number. This number is located on the bottom of each
page, in front of the page number. The numbering convention for the DS number is
“DSXXXXXXXXA”, where “XXXXXXXX” is the document number and “A” is the revision level
of the document.
For the most up-to-date information on development tools, see the MPLAB® IDE online help.
Select the Help menu, and then Topics to open a list of available online help files.
INTRODUCTION
This chapter contains general information that will be useful to know before using 16-bit
libraries. Items discussed include:
•
•
•
•
•
•
Document Layout
Conventions Used in this Guide
Recommended Reading
The Microchip Web Site
Development Systems Customer Change Notification Service
Customer Support
DOCUMENT LAYOUT
This document describes how to use GNU language tools to write code for 16-bit
applications. The document is organized in the following order:
• Chapter 1: Library Overview – gives an overview of libraries. Some are described
further in this document, while others are described in other documents or online
Help files.
• Chapter 2: Standard C Libraries – lists the library functions and macros for standard C operation.
• Chapter 3: Standard C Libraries – Math Functions – lists the math functions for
standard C operation.
• Chapter 4: Standard C Libraries – Support Functions – lists standard C library
helper functions.
• Chapter 5: Fixed-Point Math Functions – lists the fixed-point library math
functions.
• Appendix A: ASCII Character Set
 2004-2014 Microchip Technology Inc.
DS50001456J-page 5
16-Bit Language Tools Libraries
CONVENTIONS USED IN THIS GUIDE
The following conventions may appear in this documentation:
DOCUMENTATION CONVENTIONS
Description
Represents
Examples
Arial font:
MPLAB® IDE User’s Guide
Italic
Referenced books
Emphasized text
...is the only compiler...
Initial caps
A window
the Output window
A dialog
the Settings dialog
A menu selection
select Enable Programmer
Quotes
A field name in a window or
dialog
“Save project before build”
Underlined, italic with right
angle bracket
A menu path
File>Save
Bold
A dialog button
Click OK
A tab
Click the Power tab
A key on the keyboard
Press <Enter>, <F1>
Sample source code
#define START
Filenames
autoexec.bat
File paths
c:\mcc18\h
Keywords
_asm, _endasm, static
Command-line options
-Opa+, -Opa-
Bit values
0, 1
Constants
0xFF, ’A’
Italic
A variable argument
file.o, where file can be
any valid filename
Square brackets [ ]
Optional arguments
mpasmwin [options]
file [options]
Curly brackets and pipe
character: { | }
Choice of mutually exclusive
arguments; an OR selection
errorlevel {0|1}
Ellipses...
Replaces repeated text
var_name [,
var_name...]
Represents code supplied by
user
void main (void)
{ ...
}
Text in angle brackets < >
Courier New font:
Plain
DS50001456J-page 6
 2004-2014 Microchip Technology Inc.
Preface
RECOMMENDED READING
This documentation describes how to use 16-bit libraries. Other useful documents are
listed below. The following Microchip documents are available and recommended as
supplemental reference resources.
Readme Files
For the latest information on Microchip tools, read the associated Readme files (HTML
files) included with the software.
16-Bit Language Tools Getting Started (DS70094)
A guide to installing and working with the Microchip language tools for 16-bit devices.
Examples using the 16-bit simulator SIM30 (a component of MPLAB SIM) are
provided.
MPLAB® Assembler, Linker and Utilities for PIC24 MCUs and dsPIC® DSCs
User’s Guide (DS51317)
A guide to using the 16-bit assembler, object linker and various utilities, including the
16-bit archiver/librarian.
MPLAB® C Compiler for PIC24 MCUs and dsPIC® DSCs User’s Guide (DS51284)
A guide to using the 16-bit C compiler. The 16-bit linker is used with this tool.
Device-Specific Documentation
The Microchip website contains many documents that describe 16-bit device functions
and features. Among these are:
• Individual and family data sheets
• Family reference manuals
• Programmer’s reference manuals
C Standards Information
American National Standard for Information Systems – Programming Language – C.
American National Standards Institute (ANSI), 11 West 42nd. Street, New York,
New York, 10036.
This standard specifies the form and establishes the interpretation of programs
expressed in the programming language C. Its purpose is to promote portability,
reliability, maintainability and efficient execution of C language programs on a
variety of computing systems.
C Reference Manuals
Harbison, Samuel P. and Steele, Guy L., C A Reference Manual, Fourth Edition,
Prentice-Hall, Englewood Cliffs, N.J. 07632.
Kernighan, Brian W. and Ritchie, Dennis M., The C Programming Language, Second
Edition. Prentice Hall, Englewood Cliffs, N.J. 07632.
Kochan, Steven G., Programming In ANSI C, Revised Edition. Hayden Books,
Indianapolis, Indiana 46268.
Plauger, P.J., The Standard C Library, Prentice-Hall, Englewood Cliffs, N.J. 07632.
Van Sickle, Ted., Programming Microcontrollers in C, First Edition. LLH Technology
Publishing, Eagle Rock, Virginia 24085.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 7
16-Bit Language Tools Libraries
THE MICROCHIP WEB SITE
Microchip provides online support via our web site at www.microchip.com. This web
site is used as a means to make files and information easily available to customers.
Accessible by using your favorite Internet browser, the web site contains the following
information:
• Product Support – Data sheets and errata, application notes and sample
programs, design resources, user’s guides and hardware support documents,
latest software releases and archived software
• General Technical Support – Frequently Asked Questions (FAQs), technical
support requests, online discussion groups, Microchip consultant program
member listing
• Business of Microchip – Product selector and ordering guides, latest Microchip
press releases, listing of seminars and events, listings of Microchip sales offices,
distributors and factory representatives
DEVELOPMENT SYSTEMS CUSTOMER CHANGE NOTIFICATION SERVICE
Microchip’s customer notification service helps keep customers current on Microchip
products. Subscribers will receive e-mail notification whenever there are changes,
updates, revisions or errata related to a specified product family or development tool of
interest.
To register, access the Microchip web site at www.microchip.com, click on Customer
Change Notification and follow the registration instructions.
The Development Systems product group categories are:
• Compilers – The latest information on Microchip C compilers, assemblers, linkers
and other language tools. These include all MPLAB C compilers; all MPLAB
assemblers (including MPASM™ assembler); all MPLAB linkers (including
MPLINK™ object linker); and all MPLAB librarians (including MPLIB™ object
librarian).
• Emulators – The latest information on Microchip in-circuit emulators.This
includes the MPLAB REAL ICE™ and MPLAB ICE 2000 in-circuit emulators.
• In-Circuit Debuggers – The latest information on the Microchip in-circuit
debuggers. This includes MPLAB ICD 3 in-circuit debuggers and PICkit™ 3
debug express.
• MPLAB® IDE – The latest information on Microchip MPLAB IDE, the Windows®
Integrated Development Environment for development systems tools. This list is
focused on the MPLAB IDE, MPLAB IDE Project Manager, MPLAB Editor and
MPLAB SIM simulator, as well as general editing and debugging features.
• Programmers – The latest information on Microchip programmers. These include
production programmers such as MPLAB REAL ICE in-circuit emulator, MPLAB
ICD 3 in-circuit debugger and MPLAB PM3 device programmers. Also included
are nonproduction development programmers such as PICSTART® Plus and
PICkit 2 and 3.
DS50001456J-page 8
 2004-2014 Microchip Technology Inc.
Preface
CUSTOMER SUPPORT
Users of Microchip products can receive assistance through several channels:
•
•
•
•
Distributor or Representative
Local Sales Office
Field Application Engineer (FAE)
Technical Support
Customers should contact their distributor, representative or field application engineer
(FAE) for support. Local sales offices are also available to help customers. A listing of
sales offices and locations is included in the back of this document.
Technical support is available through the web site at:
http://www.microchip.com/support.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 9
16-Bit Language Tools Libraries
NOTES:
DS50001456J-page 10
 2004-2014 Microchip Technology Inc.
16-BIT LANGUAGE TOOLS
LIBRARIES
Chapter 1. Library Overview
1.1
INTRODUCTION
A library is a collection of functions grouped for reference and ease of linking. See the
“MPLAB® XC16 Assembler, Linker and Utilities User’s Guide” (DS50002106) for more
information about making and using libraries.
1.1.1
Compiler Installation Locations
The majority of the libraries discussed in this manual come with the MPLAB® XC16
C Compiler, which is installed by default in the following locations:
•
•
•
•
Windows OS 32-bit - C:\Program Files\Microchip\xc16\x.xx
Windows OS 64-bit - C:\Program Files (x86)\Microchip\xc16\x.xx
Mac OS - Applications/microchip/xc16/x.xx
Linux OS - /opt/microchip/xc16/x.xx
(where x.xx is the version number).
1.1.2
Assembly Code Applications
Free versions of the 16-bit language tool libraries are available from the Microchip web
site. DSP and 16-bit peripheral libraries are provided with object files and source code.
A math library (containing functions from the standard C header file <math.h>) is
provided as an object file only. The complete standard C library is provided with the
MPLAB XC16 C Compiler.
1.1.3
C Code Applications
The 16-bit language tool libraries are included in the lib subdirectory of the MPLAB
XC16 C Compiler install directory (Section 1.1.1 “Compiler Installation Locations”).
These libraries can be linked directly into an application with a 16-bit linker.
1.1.4
Chapter Organization
This chapter is organized in the following order:
•
•
•
•
•
•
•
OMF-Specific Libraries/Start-up Modules
Start-up Code
DSP Library
16-Bit Peripheral Libraries
Standard C Libraries with Math and Support Functions
Fixed-Point Math Functions
Compiler Built-in Functions
 2004-2014 Microchip Technology Inc.
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16-Bit Language Tools Libraries
1.2
OMF-SPECIFIC LIBRARIES/START-UP MODULES
Library files and start-up modules are specific to OMF (Object Module Format). An
OMF can be one of the following:
• COFF – This is the default.
• ELF – The debugging format used for ELF object files is DWARF 2.0.
There are two ways to select the OMF:
1. Set an environment variable called XC16_OMF for all tools.
2. Select the OMF on the command line when invoking the tool, i.e., -omf=omf or
-momf=omf.
16-bit tools will first look for generic library files when building your application (no OMF
specification). If these cannot be found, the tools will look at your OMF specifications
and determine which library file to use.
As an example, if libdsp.a is not found and no environment variable or command-line
option is set, the file, libdsp-coff.a, will be used by default.
1.3
START-UP CODE
In order to initialize variables in data memory, the linker creates a data initialization
template. This template must be processed at start-up, before the application proper
takes control. For C programs, this function is performed by the start-up modules in
libpic30-coff.a (either crt0.o or crt1.o) or libpic30-elf.a (either crt0.eo or
crt1.eo). Assembly language programs can utilize these modules directly by linking
with the desired start-up module file. The source code for the start-up modules is
provided in corresponding .s files.
The primary start-up module (crt0) initializes all variables (variables without initializers
are set to zero as required by the ANSI standard) except for variables in the persistent
data section. The alternate start-up module (crt1) performs no data initialization.
For more on start-up code, see the “MPLAB® XC16 Assembler, Linker and Utilities
User’s Guide” (DS52106) and, for C applications, the “MPLAB® XC16 C Compiler
User’s Guide” (DS00052071).
1.4
DSP LIBRARY
The DSP library (libdsp-omf.a) provides a set of digital signal processing operations
to a program targeted for execution on a dsPIC30F digital signal controller (DSC). In
total, 49 functions are supported by the DSP Library.
Documentation for these libraries is provided in HTML Help files. Examples of use may
also provided. By default, the documentation is found in the docs\dsp_lib subdirectory of the MPLAB XC16 C Compiler install directory (see Section 1.1.1 “Compiler
Installation Locations”).
1.5
16-BIT PERIPHERAL LIBRARIES
The 16-bit software and hardware peripheral libraries provide functions and macros for
setting up and controlling 16-bit peripherals. These libraries are processor-specific and
of the form libpDevice-omf.a, where Device is the 16-bit device number (e.g.,
libp30F6014-coff.a for the dsPIC30F6014 device) and omf is either coff or elf.
Documentation for these libraries is provided in HTML Help files. Examples of use are
also provided in each file. By default, the documentation is found in the
docs\periph_lib subdirectory of the MPLAB XC16 C Compiler install directory (see
Section 1.1.1 “Compiler Installation Locations”).
DS50001456J-page 12
 2004-2014 Microchip Technology Inc.
Library Overview
1.6
STANDARD C LIBRARIES WITH MATH AND SUPPORT FUNCTIONS
A complete set of ANSI-89 conforming libraries are provided. The standard C library
files are libc-omf.a (written by Dinkumware, an industry leader) and libm-omf.a
(math functions, written by Microchip).
Additionally, some 16-bit standard C library helper functions, and standard functions
that must be modified for use with 16-bit devices, are in libpic30-omf.a.
A typical C application will require these libraries. Documentation for these library
functions is contained in this manual.
1.7
FIXED-POINT MATH FUNCTIONS
Fixed-point math functions may be found in the library file libq-omf.a. Documentation
for these library functions is contained in this manual.
1.8
COMPILER BUILT-IN FUNCTIONS
The MPLAB XC16 C Compiler contains built-in functions that, to the developer, work
like library functions. These functions are listed in the “MPLAB® XC16 C Compiler
Users’ Guide” (DS50002071).
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16-Bit Language Tools Libraries
NOTES:
DS50001456J-page 14
 2004-2014 Microchip Technology Inc.
16-BIT LANGUAGE TOOLS
LIBRARIES
Chapter 2. Standard C Libraries
2.1
INTRODUCTION
Standard ANSI C library functions are contained in the file libc-omf.a, where omf will
be coff or elf depending upon the selected object module format.
2.1.1
Assembly Code Applications
A free version of the math functions library and header file is available from the
Microchip web site. No source code is available with this free version.
2.1.2
C Code Applications
The MPLAB XC16 C Compiler install directory (Section 1.1.1 “Compiler Installation
Locations”) contains the following subdirectories with library-related files:
• lib – standard C library files
• src\libm – source code for math library functions, batch file to rebuild the library
• support\h – header files for libraries
In addition, there is a file, ResourceGraphs.pdf, which contains diagrams of resources
used by each function, located in lib.
2.1.3
Chapter Organization
This chapter is organized as follows:
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Using the Standard C Libraries
<assert.h> diagnostics
<ctype.h> character handling
<errno.h> errors
<float.h> floating-point characteristics
<limits.h> implementation-defined limits
<locale.h> localization
<setjmp.h> non-local jumps
<signal.h> signal handling
<stdarg.h> variable argument lists
<stddef.h> common definitions
<stdio.h> input and output
<stdlib.h> utility functions
<string.h> string functions
<time.h> date and time functions
 2004-2014 Microchip Technology Inc.
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16-Bit Language Tools Libraries
2.2
USING THE STANDARD C LIBRARIES
Building an application which utilizes the standard C libraries requires two types of files:
header files and library files.
2.2.1
Header Files
All standard C library entities are declared or defined in one or more standard headers
(See list in Section 2.1.3 “Chapter Organization”.) To make use of a library entity in
a program, write an include directive that names the relevant standard header.
The contents of a standard header is included by naming it in an include directive, as in:
#include <stdio.h> /* include I/O facilities */
The standard headers can be included in any order. Do not include a standard header
within a declaration. Do not define macros that have the same names as keywords
before including a standard header.
A standard header never includes another standard header.
2.2.2
Library Files
The archived library files contain all the individual object files for each library function.
When linking an application, the library file must be provided as an input to the linker
(using the --library or -l linker option) such that the functions used by the
application may be linked into the application.
A typical C application will require three library files: libc-omf.a, libm-omf.a, and
libpic30-omf.a. (See Section 1.2 “OMF-Specific Libraries/Start-up Modules” for
more on OMF-specific libraries.) These libraries will be included automatically if linking
is performed using the compiler.
Note:
DS50001456J-page 16
Some standard library functions require a heap. These include the standard
I/O functions that open files and the memory allocation functions. See the
“MPLAB® XC16 Assembler, Linker and Utilities User’s Guide” (DS52106)
and “MPLAB® XC16 C Compiler User’s Guide” (DS00052071) for more
information on the heap.
 2004-2014 Microchip Technology Inc.
Standard C Libraries
2.3
<ASSERT.H> DIAGNOSTICS
The header file assert.h consists of a single macro that is useful for debugging logic
errors in programs. By using the assert statement in critical locations where certain
conditions should be true, the logic of the program may be tested.
Assertion testing may be turned off without removing the code by defining NDEBUG
before including <assert.h>. If the macro NDEBUG is defined, assert() is ignored and
no code is generated.
assert
Description:
If the expression is false, an assertion message is printed to stderr and
the program is aborted.
Include:
<assert.h>
Prototype:
void assert(int expression);
Argument:
expression The expression to test.
Remarks:
The expression evaluates to zero or non-zero. If zero, the assertion
fails and a message is printed to stderr. The message includes the
source file name (__FILE__), the source line number (__LINE__),
the expression being evaluated and the message. The macro then calls
the function abort(). If the macro _VERBOSE_DEBUGGING is defined,
a message will be printed to stderr each time assert() is called.
Example:
#include <assert.h> /* for assert */
int main(void)
{
int a;
a = 2 * 2;
assert(a == 4); /* if true-nothing prints */
assert(a == 6); /* if false-print message */
/* and abort */
}
Output:
sampassert.c:9 a == 6 -- assertion failed
ABRT
with _VERBOSE_DEBUGGING defined:
sampassert.c:8 a == 4 -- OK
sampassert.c:9 a == 6 -- assertion failed
ABRT
 2004-2014 Microchip Technology Inc.
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16-Bit Language Tools Libraries
2.4
<CTYPE.H> CHARACTER HANDLING
The header file ctype.h consists of functions that are useful for classifying and
mapping characters. Characters are interpreted according to the Standard C locale.
isalnum
Description:
Test for an alphanumeric character.
Include:
<ctype.h>
Prototype:
int isalnum(int c);
Argument:
c
Return Value:
Returns a non-zero integer value if the character is alphanumeric;
otherwise, returns a zero.
Remarks:
Alphanumeric characters are included within the ranges A-Z, a-z or 0-9.
Example:
#include <ctype.h> /* for isalnum */
#include <stdio.h> /* for printf */
The character to test.
int main(void)
{
int ch;
ch = '3';
if (isalnum(ch))
printf("3 is an alphanumeric\n");
else
printf("3 is NOT an alphanumeric\n");
ch = '#';
if (isalnum(ch))
printf("# is an alphanumeric\n");
else
printf("# is NOT an alphanumeric\n");
}
Output:
3 is an alphanumeric
# is NOT an alphanumeric
isalpha
DS50001456J-page 18
Description:
Test for an alphabetic character.
Include:
<ctype.h>
Prototype:
int isalpha(int c);
Argument:
c
Return Value:
Returns a non-zero integer value if the character is alphabetic;
otherwise, returns zero.
Remarks:
Alphabetic characters are included within the ranges A-Z or a-z.
The character to test.
 2004-2014 Microchip Technology Inc.
Standard C Libraries
isalpha (Continued)
Example:
#include <ctype.h> /* for isalpha */
#include <stdio.h> /* for printf */
int main(void)
{
int ch;
ch = 'B';
if (isalpha(ch))
printf("B is alphabetic\n");
else
printf("B is NOT alphabetic\n");
ch = '#';
if (isalpha(ch))
printf("# is alphabetic\n");
else
printf("# is NOT alphabetic\n");
}
Output:
B is alphabetic
# is NOT alphabetic
iscntrl
Description:
Test for a control character.
Include:
<ctype.h>
Prototype:
int iscntrl(int c);
Argument:
c
Return Value:
Returns a non-zero integer value if the character is a control character;
otherwise, returns zero.
Remarks:
A character is considered to be a control character if its ASCII value is
in the range 0x00 to 0x1F inclusive, or 0x7F.
Example:
#include <ctype.h> /* for iscntrl */
#include <stdio.h> /* for printf */
character to test.
int main(void)
{
char ch;
ch = 'B';
if (iscntrl(ch))
printf("B is a control character\n");
else
printf("B is NOT a control character\n");
ch = '\t';
if (iscntrl(ch))
printf("A tab is a control character\n");
else
printf("A tab is NOT a control character\n");
}
Output:
B is NOT a control character
a tab is a control character
 2004-2014 Microchip Technology Inc.
DS50001456J-page 19
16-Bit Language Tools Libraries
isdigit
Description:
Test for a decimal digit.
Include:
<ctype.h>
Prototype:
int isdigit(int c);
Argument:
c
Return Value:
Returns a non-zero integer value if the character is a digit; otherwise,
returns zero.
Remarks:
A character is considered to be a digit character if it is in the range of
‘0’-‘9’.
Example:
#include <ctype.h> /* for isdigit */
#include <stdio.h> /* for printf */
character to test.
int main(void)
{
int ch;
ch = '3';
if (isdigit(ch))
printf("3 is a digit\n");
else
printf("3 is NOT a digit\n");
ch = '#';
if (isdigit(ch))
printf("# is a digit\n");
else
printf("# is NOT a digit\n");
}
Output:
3 is a digit
# is NOT a digit
isgraph
Description:
Test for a graphical character.
Include:
<ctype.h>
Prototype:
int isgraph (int c);
Argument:
c
Return Value:
Returns a non-zero integer value if the character is a graphical
character; otherwise, returns zero.
Remarks:
A character is considered to be a graphical character if it is any
printable character except a space.
Example:
#include <ctype.h> /* for isgraph */
#include <stdio.h> /* for printf */
character to test
int main(void)
{
int ch;
DS50001456J-page 20
 2004-2014 Microchip Technology Inc.
Standard C Libraries
isgraph (Continued)
ch = '3';
if (isgraph(ch))
printf("3 is a graphical character\n");
else
printf("3 is NOT a graphical character\n");
ch = '#';
if (isgraph(ch))
printf("# is a graphical character\n");
else
printf("# is NOT a graphical character\n");
ch = ' ';
if (isgraph(ch))
printf("a space is a graphical character\n");
else
printf("a space is NOT a graphical character\n");
}
Output:
3 is a graphical character
# is a graphical character
a space is NOT a graphical character
islower
Description:
Test for a lowercase alphabetic character.
Include:
<ctype.h>
Prototype:
int islower (int c);
Argument:
c
Return Value:
Returns a non-zero integer value if the character is a lowercase
alphabetic character; otherwise, returns zero.
Remarks:
A character is considered to be a lowercase alphabetic character if it is
in the range of ‘a’-‘z’.
Example:
#include <ctype.h> /* for islower */
#include <stdio.h> /* for printf */
character to test
int main(void)
{
int ch;
ch = 'B';
if (islower(ch))
printf("B is lowercase\n");
else
printf("B is NOT lowercase\n");
ch = 'b';
if (islower(ch))
printf("b is lowercase\n");
else
printf("b is NOT lowercase\n");
}
 2004-2014 Microchip Technology Inc.
DS50001456J-page 21
16-Bit Language Tools Libraries
islower (Continued)
Output:
B is NOT lowercase
b is lowercase
isprint
Description:
Test for a printable character (includes a space).
Include:
<ctype.h>
Prototype:
int isprint (int c);
Argument:
c
Return Value:
Returns a non-zero integer value if the character is printable;
otherwise, returns zero.
Remarks:
A character is considered to be a printable character if it is in the range
0x20 to 0x7e inclusive.
Example:
#include <ctype.h> /* for isprint */
#include <stdio.h> /* for printf */
character to test
int main(void)
{
int ch;
ch = '&';
if (isprint(ch))
printf("& is a printable character\n");
else
printf("& is NOT a printable character\n");
ch = '\t';
if (isprint(ch))
printf("a tab is a printable character\n");
else
printf("a tab is NOT a printable character\n");
}
Output:
& is a printable character
a tab is NOT a printable character
ispunct
DS50001456J-page 22
Description:
Test for a punctuation character.
Include:
<ctype.h>
Prototype:
int ispunct (int c);
Argument:
c
Return Value:
Returns a non-zero integer value if the character is a punctuation
character; otherwise, returns zero.
Remarks:
A character is considered to be a punctuation character if it is a printable
character which is neither a space nor an alphanumeric character.
Punctuation characters consist of the following:
!"#$%&'();<=>?@[\]*+,-./:^_{|}~
character to test
 2004-2014 Microchip Technology Inc.
Standard C Libraries
ispunct (Continued)
Example:
#include <ctype.h> /* for ispunct */
#include <stdio.h> /* for printf */
int main(void)
{
int ch;
ch = '&';
if (ispunct(ch))
printf("& is a punctuation character\n");
else
printf("& is NOT a punctuation character\n");
ch = '\t';
if (ispunct(ch))
printf("a tab is a punctuation character\n");
else
printf("a tab is NOT a punctuation character\n");
}
Output:
& is a punctuation character
a tab is NOT a punctuation character
isspace
Description:
Test for a white-space character.
Include:
<ctype.h>
Prototype:
int isspace (int c);
Argument:
c
Return Value:
Returns a non-zero integer value if the character is a white-space
character; otherwise, returns zero.
Remarks:
A character is considered to be a white-space character if it is one of
the following: space (' '), form feed ('\f'), newline ('\n'), carriage return
('\r'), horizontal tab ('\t'), or vertical tab ('\v').
Example:
#include <ctype.h> /* for isspace */
#include <stdio.h> /* for printf */
character to test
int main(void)
{
int ch;
ch = '&';
if (isspace(ch))
printf("& is a white-space character\n");
else
printf("& is NOT a white-space character\n");
ch = '\t';
if (isspace(ch))
printf("a tab is a white-space character\n");
else
printf("a tab is NOT a white-space character\n");
}
 2004-2014 Microchip Technology Inc.
DS50001456J-page 23
16-Bit Language Tools Libraries
isspace (Continued)
Output:
& is NOT a white-space character
a tab is a white-space character
isupper
Description:
Test for an uppercase letter.
Include:
<ctype.h>
Prototype:
int isupper (int c);
Argument:
c
Return Value:
Returns a non-zero integer value if the character is an uppercase
alphabetic character; otherwise, returns zero.
Remarks:
A character is considered to be an uppercase alphabetic character if it
is in the range of ‘A’-‘Z’.
Example:
#include <ctype.h> /* for isupper */
#include <stdio.h> /* for printf */
character to test
int main(void)
{
int ch;
ch = 'B';
if (isupper(ch))
printf("B is uppercase\n");
else
printf("B is NOT uppercase\n");
ch = 'b';
if (isupper(ch))
printf("b is uppercase\n");
else
printf("b is NOT uppercase\n");
}
Output:
B is uppercase
b is NOT uppercase
isxdigit
DS50001456J-page 24
Description:
Test for a hexadecimal digit.
Include:
<ctype.h>
Prototype:
int isxdigit (int c);
Argument:
c
Return Value:
Returns a non-zero integer value if the character is a hexadecimal digit;
otherwise, returns zero.
Remarks:
A character is considered to be a hexadecimal digit character if it is in
the range of ‘0’-‘9’, ‘A’-‘F’, or ‘a’-‘f’. Note: The list does not include the
leading 0x because 0x is the prefix for a hexadecimal number but is not
an actual hexadecimal digit.
character to test
 2004-2014 Microchip Technology Inc.
Standard C Libraries
isxdigit (Continued)
Example:
#include <ctype.h> /* for isxdigit */
#include <stdio.h> /* for printf */
int main(void)
{
int ch;
ch = 'B';
if (isxdigit(ch))
printf("B is a hexadecimal digit\n");
else
printf("B is NOT a hexadecimal digit\n");
ch = 't';
if (isxdigit(ch))
printf("t is a hexadecimal digit\n");
else
printf("t is NOT a hexadecimal digit\n");
}
Output:
B is a hexadecimal digit
t is NOT a hexadecimal digit
tolower
Description:
Convert a character to a lowercase alphabetical character.
Include:
<ctype.h>
Prototype:
int tolower (int c);
Argument:
c
Return Value:
Returns the corresponding lowercase alphabetical character if the
argument was originally uppercase; otherwise, returns the original
character.
Remarks:
Only uppercase alphabetical characters may be converted to lowercase.
Example:
#include <ctype.h> /* for tolower */
#include <stdio.h> /* for printf */
The character to convert to lowercase.
int main(void)
{
int ch;
ch = 'B';
printf("B changes to lowercase %c\n",
tolower(ch));
ch = 'b';
printf("b remains lowercase %c\n",
tolower(ch));
ch = '@';
printf("@ has no lowercase, ");
printf("so %c is returned\n", tolower(ch));
}
 2004-2014 Microchip Technology Inc.
DS50001456J-page 25
16-Bit Language Tools Libraries
tolower (Continued)
Output:
B changes to lowercase b
b remains lowercase b
@ has no lowercase, so @ is returned
toupper
Description:
Convert a character to an uppercase alphabetical character.
Include:
<ctype.h>
Prototype:
int toupper (int c);
Argument:
c
Return Value:
Returns the corresponding uppercase alphabetical character if the
argument was originally lowercase; otherwise, returns the original character.
Remarks:
Only lowercase alphabetical characters may be converted to uppercase.
Example:
#include <ctype.h> /* for toupper */
#include <stdio.h> /* for printf */
The character to convert to uppercase.
int main(void)
{
int ch;
ch = 'b';
printf("b changes to uppercase %c\n",
toupper(ch));
ch = 'B';
printf("B remains uppercase %c\n",
toupper(ch));
ch = '@';
printf("@ has no uppercase, ");
printf("so %c is returned\n", toupper(ch));
}
Output:
b changes to uppercase B
B remains uppercase B
@ has no uppercase, so @ is returned
DS50001456J-page 26
 2004-2014 Microchip Technology Inc.
Standard C Libraries
2.5
<ERRNO.H> ERRORS
The header file errno.h consists of macros that provide error codes that are reported
by certain library functions (see individual functions). The variable errno may return
any value greater than zero. To test if a library function encounters an error, the
program should store the zero value in errno immediately before calling the library
function. The value should be checked before another function call could change the
value. At program start-up, errno is zero. Library functions will never set errno to zero.
EDOM
Description:
Represents a domain error.
Include:
<errno.h>
Remarks:
EDOM represents a domain error, which occurs when an input argument
is outside the domain in which the function is defined.
ERANGE
Description:
Represents an overflow or underflow error.
Include:
<errno.h>
Remarks:
ERANGE represents an overflow or underflow error, which occurs when
a result is too large or too small to be stored.
errno
Description:
Contains the value of an error when an error occurs in a function.
Include:
<errno.h>
Remarks:
The variable errno is set to a non-zero integer value by a library function when an error occurs. At program start-up, errno is set to zero.
Errno should be reset to zero prior to calling a function that sets it.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 27
16-Bit Language Tools Libraries
2.6
<FLOAT.H> FLOATING-POINT CHARACTERISTICS
The header file float.h consists of macros that specify various properties of
floating-point types. These properties include number of significant figures, size limits
and what rounding mode is used.
DBL_DIG
Description:
Number of decimal digits of precision in a double precision
floating-point value.
Include:
<float.h>
Value:
6 by default, 15 if the switch -fno-short-double is used
Remarks:
By default, a double type is the same size as a float type (32-bit representation). The -fno-short-double switch allows the IEEE 64-bit
representation to be used for a double precision floating-point value.
DBL_EPSILON
Description:
The difference between 1.0 and the next larger representable double
precision floating-point value
Include:
<float.h>
Value:
1.192093e-07 by default, 2.220446e-16 if the switch
-fno-short-double is used
Remarks:
By default, a double type is the same size as a float type (32-bit representation). The -fno-short-double switch allows the IEEE 64-bit
representation to be used for a double precision floating-point value.
DBL_MANT_DIG
Description:
Number of base-FLT_RADIX digits in a double precision floating-point
significand.
Include:
<float.h>
Value:
24 by default, 53 if the switch -fno-short-double is used
Remarks:
By default, a double type is the same size as a float type (32-bit representation). The -fno-short-double switch allows the IEEE 64-bit
representation to be used for a double precision floating-point value.
DBL_MAX
DS50001456J-page 28
Description:
Maximum finite double precision floating-point value.
Include:
<float.h>
Value:
3.402823e+38 by default, 1.797693e+308 if the switch
-fno-short-double is used
Remarks:
By default, a double type is the same size as a float type (32-bit representation). The -fno-short-double switch allows the IEEE 64-bit
representation to be used for a double precision floating-point value.
 2004-2014 Microchip Technology Inc.
Standard C Libraries
DBL_MAX_10_EXP
Description:
Maximum integer value for a double precision floating-point exponent in
base 10.
Include:
<float.h>
Value:
38 by default, 308 if the switch -fno-short-double is used
Remarks:
By default, a double type is the same size as a float type (32-bit representation). The -fno-short-double switch allows the IEEE 64-bit
representation to be used for a double precision floating-point value.
DBL_MAX_EXP
Description:
Maximum integer value for a double precision floating-point exponent in
base FLT_RADIX.
Include:
<float.h>
Value:
128 by default, 1024 if the switch -fno-short-double is used
Remarks:
By default, a double type is the same size as a float type (32-bit representation). The -fno-short-double switch allows the IEEE 64-bit
representation to be used for a double precision floating-point value.
DBL_MIN
Description:
Minimum double precision floating-point value.
Include:
<float.h>
Value:
1.175494e-38 by default, 2.225074e-308 if the switch
-fno-short-double is used
Remarks:
By default, a double type is the same size as a float type (32-bit representation). The -fno-short-double switch allows the IEEE 64-bit
representation to be used for a double precision floating-point value.
DBL_MIN_10_EXP
Description:
Minimum negative integer value for a double precision floating-point
exponent in base 10.
Include:
<float.h>
Value:
-37 by default, -307 if the switch -fno-short-double is used
Remarks:
By default, a double type is the same size as a float type (32-bit representation). The -fno-short-double switch allows the IEEE 64-bit
representation to be used for a double precision floating-point value.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 29
16-Bit Language Tools Libraries
DBL_MIN_EXP
Description:
Minimum negative integer value for a double precision floating-point
exponent in base FLT_RADIX.
Include:
<float.h>
Value:
-125 by default, -1021 if the switch -fno-short-double is used
Remarks:
By default, a double type is the same size as a float type (32-bit representation). The -fno-short-double switch allows the IEEE 64-bit
representation to be used for a double precision floating-point value.
FLT_DIG
Description:
Number of decimal digits of precision in a single precision floating-point
value.
Include:
<float.h>
Value:
6
FLT_EPSILON
Description:
The difference between 1.0 and the next larger representable single
precision floating-point value.
Include:
<float.h>
Value:
1.192093e-07
FLT_MANT_DIG
Description:
Number of base-FLT_RADIX digits in a single precision floating-point
significand.
Include:
<float.h>
Value:
24
FLT_MAX
Description:
Maximum finite single precision floating-point value.
Include:
<float.h>
Value:
3.402823e+38
FLT_MAX_10_EXP
DS50001456J-page 30
Description:
Maximum integer value for a single precision floating-point exponent in
base 10.
Include:
<float.h>
Value:
38
 2004-2014 Microchip Technology Inc.
Standard C Libraries
FLT_MAX_EXP
Description:
Maximum integer value for a single precision floating-point exponent in
base FLT_RADIX.
Include:
<float.h>
Value:
128
FLT_MIN
Description:
Minimum single precision floating-point value.
Include:
<float.h>
Value:
1.175494e-38
FLT_MIN_10_EXP
Description:
Minimum negative integer value for a single precision floating-point
exponent in base 10.
Include:
<float.h>
Value:
-37
FLT_MIN_EXP
Description:
Minimum negative integer value for a single precision floating-point
exponent in base FLT_RADIX.
Include:
<float.h>
Value:
-125
FLT_RADIX
Description:
Radix of exponent representation.
Include:
<float.h>
Value:
2
Remarks:
The base representation of the exponent is base-2 or binary.
FLT_ROUNDS
Description:
Represents the rounding mode for floating-point operations.
Include:
<float.h>
Value:
1
Remarks:
Rounds to the nearest representable value.
LDBL_DIG
Description:
Number of decimal digits of precision in a long double precision
floating-point value.
Include:
<float.h>
Value:
15
 2004-2014 Microchip Technology Inc.
DS50001456J-page 31
16-Bit Language Tools Libraries
LDBL_EPSILON
Description:
The difference between 1.0 and the next larger representable long
double precision floating-point value.
Include:
<float.h>
Value:
2.220446e-16
LDBL_MANT_DIG
Description:
Number of base-FLT_RADIX digits in a long double precision
floating-point significand.
Include:
<float.h>
Value:
53
LDBL_MAX
Description:
Maximum finite long double precision floating-point value.
Include:
<float.h>
Value:
1.797693e+308
LDBL_MAX_10_EXP
Description:
Maximum integer value for a long double precision floating-point
exponent in base 10.
Include:
<float.h>
Value:
308
LDBL_MAX_EXP
Description:
Maximum integer value for a long double precision floating-point
exponent in base FLT_RADIX.
Include:
<float.h>
Value:
1024
LDBL_MIN
Description:
Minimum long double precision floating-point value.
Include:
<float.h>
Value:
2.225074e-308
LDBL_MIN_10_EXP
DS50001456J-page 32
Description:
Minimum negative integer value for a long double precision
floating-point exponent in base 10.
Include:
<float.h>
Value:
-307
 2004-2014 Microchip Technology Inc.
Standard C Libraries
LDBL_MIN_EXP
2.7
Description:
Minimum negative integer value for a long double precision
floating-point exponent in base FLT_RADIX.
Include:
<float.h>
Value:
-1021
<LIMITS.H> IMPLEMENTATION-DEFINED LIMITS
The header file limits.h consists of macros that define the minimum and maximum
values of integer types. Each of these macros can be used in #if preprocessing
directives.
CHAR_BIT
Description:
Number of bits to represent type char.
Include:
<limits.h>
Value:
8
CHAR_MAX
Description:
Maximum value of a char.
Include:
<limits.h>
Value:
127
CHAR_MIN
Description:
Minimum value of a char.
Include:
<limits.h>
Value:
-128
INT_MAX
Description:
Maximum value of an int.
Include:
<limits.h>
Value:
32767
INT_MIN
Description:
Minimum value of an int.
Include:
<limits.h>
Value:
-32768
LLONG_MAX
Description:
Maximum value of a long long int.
Include:
<limits.h>
Value:
9223372036854775807
 2004-2014 Microchip Technology Inc.
DS50001456J-page 33
16-Bit Language Tools Libraries
LLONG_MIN
Description:
Minimum value of a long long int.
Include:
<limits.h>
Value:
-9223372036854775808
LONG_MAX
Description:
Maximum value of a long int.
Include:
<limits.h>
Value:
2147483647
LONG_MIN
Description:
Minimum value of a long int.
Include:
<limits.h>
Value:
-2147483648
MB_LEN_MAX
Description:
Maximum number of bytes in a multibyte character.
Include:
<limits.h>
Value:
1
SCHAR_MAX
Description:
Maximum value of a signed char.
Include:
<limits.h>
Value:
127
SCHAR_MIN
Description:
Minimum value of a signed char.
Include:
<limits.h>
Value:
-128
SHRT_MAX
Description:
Maximum value of a short int.
Include:
<limits.h>
Value:
32767
SHRT_MIN
DS50001456J-page 34
Description:
Minimum value of a short int.
Include:
<limits.h>
Value:
-32768
 2004-2014 Microchip Technology Inc.
Standard C Libraries
UCHAR_MAX
Description:
Maximum value of an unsigned char.
Include:
<limits.h>
Value:
255
UINT_MAX
Description:
Maximum value of an unsigned int.
Include:
<limits.h>
Value:
65535
ULLONG_MAX
Description:
Maximum value of a long long unsigned int.
Include:
<limits.h>
Value:
18446744073709551615
ULONG_MAX
Description:
Maximum value of a long unsigned int.
Include:
<limits.h>
Value:
4294967295
USHRT_MAX
2.8
Description:
Maximum value of an unsigned short int.
Include:
<limits.h>
Value:
65535
<LOCALE.H> LOCALIZATION
This compiler defaults to the C locale and does not support any other locales; therefore,
it does not support the header file locale.h. The following would normally be found in
this file:
•
•
•
•
•
•
•
•
•
•
struct lconv
NULL
LC_ALL
LC_COLLATE
LC_CTYPE
LC_MONETARY
LC_NUMERIC
LC_TIME
localeconv
setlocale
 2004-2014 Microchip Technology Inc.
DS50001456J-page 35
16-Bit Language Tools Libraries
2.9
<SETJMP.H> NON-LOCAL JUMPS
The header file setjmp.h consists of a type, a macro and a function that allow control
transfers to occur that bypass the normal function call and return process.
jmp_buf
Description:
A type that is an array used by setjmp and longjmp to save and
restore the program environment.
Include:
<setjmp.h>
Prototype:
typedef int jmp_buf[_NSETJMP];
Remarks:
_NSETJMP is defined as 16 + 2 that represents 16 registers and a
32-bit return address.
setjmp
Description:
A macro that saves the current state of the program for later use by
longjmp.
Include:
<setjmp.h>
Prototype:
#define setjmp(jmp_buf env)
Argument:
env variable where environment is stored
Return Value:
If the return is from a direct call, setjmp returns zero. If the return is
from a call to longjmp, setjmp returns a non-zero value.
Note: If the argument val from longjmp is 0, setjmp returns 1.
Example:
See longjmp.
longjmp
Description:
A function that restores the environment saved by setjmp.
Include:
<setjmp.h>
Prototype:
void longjmp(jmp_buf env, int val);
Arguments:
env variable where environment is stored
val value to be returned to setjmp call.
Remarks:
DS50001456J-page 36
The value parameter, val, should be non-zero. If longjmp is invoked
from a nested signal handler (that is, invoked as a result of a signal
raised during the handling of another signal), the behavior is undefined.
 2004-2014 Microchip Technology Inc.
Standard C Libraries
2.10
<SIGNAL.H> SIGNAL HANDLING
The header file signal.h consists of a type, several macros and two functions that
specify how the program handles signals while it is executing. A signal is a condition
that may be reported during the program execution. Signals are synchronous,
occurring under software control via the raise function.
A signal may be handled by:
• Default handling (SIG_DFL); the signal is treated as a fatal error and execution
stops
• Ignoring the signal (SIG_IGN); the signal is ignored and control is returned to the
user application
• Handling the signal with a function designated via signal.
By default, all signals are handled by the default handler, which is identified by
SIG_DFL.
The type sig_atomic_t is an integer type that the program accesses atomically. When
this type is used with the keyword volatile, the signal handler can share the data
objects with the rest of the program.
sig_atomic_t
Description:
A type used by a signal handler.
Include:
<signal.h>
Prototype:
typedef int sig_atomic_t;
SIG_DFL
Description:
Used as the second argument and/or the return value for signal to
specify that the default handler should be used for a specific signal.
Include:
<signal.h>
SIG_ERR
Description:
Used as the return value for signal when it cannot complete a
request due to an error.
Include:
<signal.h>
SIG_IGN
Description:
Used as the second argument and/or the return value for signal to
specify that the signal should be ignored.
Include:
<signal.h>
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16-Bit Language Tools Libraries
SIGABRT
Description:
Name for the abnormal termination signal.
Include:
<signal.h>
Prototype:
#define SIGABRT
Remarks:
SIGABRT represents an abnormal termination signal and is used in
conjunction with raise or signal. The default raise behavior
(action identified by SIG_DFL) is to output to the standard error stream:
abort - terminating
See the example accompanying signal to see general usage of
signal names and signal handling.
Example:
#include <signal.h> /* for raise, SIGABRT */
#include <stdio.h> /* for printf */
int main(void)
{
raise(SIGABRT);
printf("Program never reaches here.");
}
Output:
ABRT
Explanation:
ABRT stands for “abort”.
SIGFPE
Description:
Signals floating-point errors such as for division by zero or result out of
range.
Include:
<signal.h>
Prototype:
#define SIGFPE
Remarks:
SIGFPE is used as an argument for raise and/or signal. When
used, the default behavior is to print an arithmetic error message and
terminate the calling program. This may be overridden by a user
function that defines the signal handler actions. See signal for an
example of a user-defined function.
Example:
#include <signal.h> /* for raise, SIGFPE */
#include <stdio.h> /* for printf */
int main(void)
{
raise(SIGFPE);
printf("Program never reaches here");
}
Output:
FPE
Explanation:
FPE stands for “floating-point error”.
DS50001456J-page 38
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Standard C Libraries
SIGILL
Description:
Signals illegal instruction.
Include:
<signal.h>
Prototype:
#define SIGILL
Remarks:
SIGILL is used as an argument for raise and/or signal. When
used, the default behavior is to print an invalid executable code message and terminate the calling program. This may be overridden by a
user function that defines the signal handler actions. See signal for
an example of a user-defined function.
Example:
#include <signal.h> /* for raise, SIGILL */
#include <stdio.h> /* for printf */
int main(void)
{
raise(SIGILL);
printf("Program never reaches here");
}
Output:
ILL
Explanation:
ILL stands for “illegal instruction”.
SIGINT
Description:
Interrupt signal.
Include:
<signal.h>
Prototype:
#define SIGINT
Remarks:
SIGINT is used as an argument for raise and/or signal. When
used, the default behavior is to print an interruption message and terminate the calling program. This may be overridden by a user function
that defines the signal handler actions. See signal for an example of
a user-defined function.
Example:
#include <signal.h> /* for raise, SIGINT */
#include <stdio.h> /* for printf */
int main(void)
{
raise(SIGINT);
printf("Program never reaches here.");
}
Output:
INT
Explanation:
INT stands for “interruption”.
 2004-2014 Microchip Technology Inc.
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16-Bit Language Tools Libraries
SIGSEGV
Description:
Signals invalid access to storage.
Include:
<signal.h>
Prototype:
#define SIGSEGV
Remarks:
SIGSEGV is used as an argument for raise and/or signal. When
used, the default behavior is to print an invalid storage request message and terminate the calling program. This may be overridden by a
user function that defines the signal handler actions. See signal for
an example of a user-defined function.
Example:
#include <signal.h> /* for raise, SIGSEGV */
#include <stdio.h> /* for printf */
int main(void)
{
raise(SIGSEGV);
printf("Program never reaches here.");
}
Output:
SEGV
Explanation:
SEGV stands for “invalid storage access”.
SIGTERM
Description:
Signals a termination request.
Include:
<signal.h>
Prototype:
#define SIGTERM
Remarks:
SIGTERM is used as an argument for raise and/or signal. When
used, the default behavior is to print a termination request message
and terminate the calling program. This may be overridden by a user
function that defines the signal handler actions. See signal for an
example of a user-defined function.
Example:
#include <signal.h> /* for raise, SIGTERM */
#include <stdio.h> /* for printf */
int main(void)
{
raise(SIGTERM);
printf("Program never reaches here.");
}
Output:
TERM
Explanation:
TERM stands for “termination request”.
DS50001456J-page 40
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Standard C Libraries
raise
Description:
Reports a synchronous signal.
Include:
<signal.h>
Prototype:
int raise(int sig);
Argument:
sig signal name
Return Value:
Returns a 0 if successful; otherwise, returns a non-zero value.
Remarks:
raise sends the signal identified by sig to the executing program.
Example:
#include <signal.h>
/*
/*
#include <stdlib.h>
/*
#include <stdio.h>
/*
#include <p30f6014.h> /*
for raise, signal,
SIGILL, SIG_DFL
for div, div_t
for printf
for INTCON1bits */
*/
*/
*/
*/
void __attribute__((__interrupt__))
_MathError(void)
{
raise(SIGILL);
INTCON1bits.MATHERR = 0;
}
void illegalinsn(int idsig)
{
printf("Illegal instruction executed\n");
exit(1);
}
int main(void)
{
int x, y;
div_t z;
signal(SIGILL, illegalinsn);
x = 7;
y = 0;
z = div(x, y);
printf("Program never reaches here");
}
Output:
Illegal instruction executed
Explanation:
This example requires the linker script, p30f6014.gld. There are
three parts to this example.
First, an interrupt handler is written for the interrupt vector,
_MathError, to handle a math error by sending an illegal instruction,
signal (SIGILL), to the executing program. The last statement in
the interrupt handler clears the exception flag.
Second, the function illegalinsn will print an error message and
call exit.
Third, in main, signal (SIGILL, illegalinsn) sets the handler
for SIGILL to the function illegalinsn.
When a math error occurs due to a divide by zero, the _MathError
interrupt vector is called, which in turn will raise a signal that will call the
handler function for SIGILL: the function illegalinsn. Thus, error
messages are printed and the program is terminated.
 2004-2014 Microchip Technology Inc.
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16-Bit Language Tools Libraries
signal
Description:
Controls interrupt signal handling.
Include:
<signal.h>
Prototype:
void (*signal(int sig, void(*func)(int)))(int);
Arguments:
sig
signal name
func
function to be executed
Return Value:
Returns the previous value of func.
Example:
#include <signal.h> /*
/*
/*
#include <stdio.h> /*
for signal, raise, */
SIGINT, SIGILL, */
SIG_IGN, and SIGFPE */
for printf */
/* Signal handler function */
void mysigint(int id)
{
printf("SIGINT received\n");
}
int main(void)
{
/* Override default with user defined function */
signal(SIGINT, mysigint);
raise(SIGINT);
/* Ignore signal handler */
signal(SIGILL, SIG_IGN);
raise(SIGILL);
printf("SIGILL was ignored\n");
/* Use default signal handler */
raise(SIGFPE);
printf("Program never reaches here.");
}
Output:
SIGINT received
SIGILL was ignored
FPE
Explanation:
The function mysigint is the user-defined signal handler for SIGINT.
Inside the main program, the function signal is called to set up the
signal handler (mysigint) for the signal SIGINT that will override the
default actions. The function raise is called to report the signal
SIGINT. This causes the signal handler for SIGINT to use the
user-defined function (mysigint) as the signal handler so it prints the
“SIGINT received” message.
Next, the function signal is called to set up the signal handler
SIG_IGN for the signal SIGILL. The constant SIG_IGN is used to indicate the signal should be ignored. The function raise is called to
report the signal SIGILL that is ignored.
The function raise is called again to report the signal SIGFPE. Since
there is no user-defined function for SIGFPE, the default signal handler
is used so the message “FPE” is printed (which stands for
“arithmetic error - terminating”). Then, the calling program
is terminated. The printf statement is never reached.
DS50001456J-page 42
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Standard C Libraries
2.11
<STDARG.H> VARIABLE ARGUMENT LISTS
The header file stdarg.h supports functions with variable argument lists. This allows
functions to have arguments without corresponding parameter declarations. There
must be at least one named argument. The variable arguments are represented by
ellipses (...). An object of type va_list must be declared inside the function to hold the
arguments. va_start will initialize the variable to an argument list, va_arg will access
the argument list and va_end will end the use of the argument.
va_list
Description:
The type va_list declares a variable that will refer to each argument
in a variable-length argument list.
Include:
<stdarg.h>
Example:
See va_arg.
va_arg
Description:
Gets the current argument.
Include:
<stdarg.h>
Prototype:
#define va_arg(va_list ap, Ty)
Argument:
ap
pointer to list of arguments
Ty
type of argument to be retrieved
Return Value:
Returns the current argument
Remarks:
va_start must be called before va_arg.
Example:
#include <stdio.h>
#include <stdarg.h>
/* for printf */
/* for va_arg, va_start,
va_list, va_end */
void tprint(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
while (*fmt)
{
switch (*fmt)
{
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va_arg (Continued)
case '%':
fmt++;
if (*fmt == 'd')
{
int d = va_arg(ap, int);
printf("<%d> is an integer\n",d);
}
else if (*fmt == 's')
{
char *s = va_arg(ap, char*);
printf("<%s> is a string\n", s);
}
else
{
printf("%%%c is an unknown format\n",
*fmt);
}
fmt++;
break;
default:
printf("%c is unknown\n", *fmt);
fmt++;
break;
}
}
va_end(ap);
}
int main(void)
{
tprint("%d%s.%c", 83, "This is text.", 'a');
}
Output:
<83> is an integer
<This is text.> is a string
. is unknown
%c is an unknown format
DS50001456J-page 44
 2004-2014 Microchip Technology Inc.
Standard C Libraries
va_end
Description:
Ends the use of ap.
Include:
<stdarg.h>
Prototype:
#define va_end(va_list ap)
Argument:
ap
Remarks:
After a call to va_end, the argument list pointer, ap, is considered to be
invalid. Further calls to va_arg should not be made until the next
va_start. In the 16-bit compiler, va_end does nothing, so this call is
not necessary but should be used for readability and portability.
Example:
See va_arg.
pointer to list of arguments
va_start
Description:
Sets the argument pointer ap to first optional argument in the
variable-length argument list.
Include:
<stdarg.h>
Prototype:
#define va_start(va_list ap, last_arg)
Argument:
ap
pointer to list of arguments
last_arg
last named argument before the optional arguments
Example:
2.12
See va_arg.
<STDDEF.H> COMMON DEFINITIONS
The header file stddef.h consists of several types and macros that are of general use
in programs.
ptrdiff_t
Description:
The type of the result of subtracting two pointers.
Include:
<stddef.h>
size_t
Description:
The type of the result of the sizeof operator.
Include:
<stddef.h>
wchar_t
Description:
A type that holds a wide character value.
Include:
<stddef.h>
NULL
Description:
The value of a null pointer constant.
Include:
<stddef.h>
 2004-2014 Microchip Technology Inc.
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16-Bit Language Tools Libraries
offsetof
Description:
Gives the offset of a structure member from the beginning of the
structure.
Include:
<stddef.h>
Prototype:
#define offsetof(T, mbr)
Arguments:
T
name of structure
mbr name of member in structure T
Return Value:
Returns the offset in bytes of the specified member (mbr) from the
beginning of the structure.
Remarks:
The macro offsetof is undefined for bitfields. An error message will
occur if bitfields are used.
Example:
#include <stddef.h> /* for offsetof */
#include <stdio.h> /* for printf */
struct info {
char item1[5];
int item2;
char item3;
float item4;
};
int main(void)
{
printf("Offset of item1
offsetof(struct
printf("Offset of item2
offsetof(struct
printf("Offset of item3
offsetof(struct
printf("Offset of item4
offsetof(struct
}
Output:
Offset
Offset
Offset
Offset
of
of
of
of
item1
item2
item3
item4
=
=
=
=
= %d\n",
info,item1));
= %d\n",
info,item2));
= %d\n",
info,item3));
= %d\n",
info,item4));
0
6
8
10
Explanation:
This program shows the offset in bytes of each structure member from
the start of the structure. Although item1 is only 5 bytes (char
item1[5]), padding is added so the address of item2 falls on an
even boundary. The same occurs with item3; it is 1 byte (char
item3) with 1 byte of padding.
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Standard C Libraries
2.13
<STDIO.H> INPUT AND OUTPUT
The header file stdio.h consists of types, macros and functions that provide support
to perform input and output operations on files and streams. When a file is opened, it
is associated with a stream. A stream is a pipeline for the flow of data into and out of
files. Because different systems use different properties, the stream provides more uniform properties to allow reading and writing of the files.
Streams can be text streams or binary streams. Text streams consist of a sequence of
characters divided into lines. Each line is terminated with a newline (‘\n’) character. The
characters may be altered in their internal representation, particularly in regards to line
endings. Binary streams consist of sequences of bytes of information. The bytes transmitted to the binary stream are not altered. There is no concept of lines - the file is just
a series of bytes.
At start-up, three streams are automatically opened: stdin, stdout and stderr. stdin
provides a stream for standard input, stdout is standard output and stderr is the standard error. Additional streams may be created with the fopen function. See fopen for
the different types of file access that are permitted. These access types are used by
fopen and freopen.
The type FILE is used to store information about each opened file stream. It includes
such things as error indicators, end-of-file indicators, file position indicators and other
internal status information needed to control a stream. Many functions in the stdio use
FILE as an argument.
There are three types of buffering: unbuffered, line buffered and fully buffered. Unbuffered means a character or byte is transferred one at a time. Line buffered collects and
transfers an entire line at a time (i.e., the newline character indicates the end of a line).
Fully buffered allows blocks of an arbitrary size to be transmitted. The functions setbuf
and setvbuf control file buffering.
The stdio.h file also contains functions that use input and output formats. The input
formats, or scan formats, are used for reading data. Their descriptions can be found
under scanf, but they are also used by fscanf and sscanf. The output formats, or print
formats, are used for writing data. Their descriptions can be found under printf.
These print formats are also used by fprintf, sprintf, vfprintf, vprintf and
vsprintf.
2.13.1
Compiler Options
Certain compiler options may affect how standard I/O performs. In an effort to provide
a more tailored version of the formatted I/O routines, the tool chain may convert a call
to a printf or scanf style function to a different call. The options are summarized
below:
•The -msmart-io option, when enabled, will attempt to convert printf, scanf
and other functions that use the input output formats to an integer-only variant.
The functionality is the same as that of the C standard forms, minus the support
for floating-point output. -msmart-io=0 disables this feature and no conversion
will take place. -msmart-io=1 or -msmart-io (the default) will convert a function call if it can be proven that an I/O function will never be presented with a
floating-point conversion. -msmart-io=2 is more optimistic than the default, and
will assume that non-constant format strings or otherwise unknown format
strings will not contain a floating-point format. In the event that -msmart-io=2 is
used with a floating-point format, the format letter will appear as literal text and
its corresponding argument will not be consumed.
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16-Bit Language Tools Libraries
•-fno-short-double will cause the compiler to generate calls to formatted I/O
routines that support double as if it were a long double type.
Mixing modules compiled with these options may result in a larger executable size or
incorrect execution if large and small double-sized data is shared across modules.
2.13.2
Customizing STDIO
The standard I/O relies on helper functions described in Chapter 4. “Standard C
Libraries - Support Functions”. These functions include read(), write(), open(),
and close() which are called to read, write, open or close handles that are associated
with standard I/O FILE pointers. The sources for these libraries are provided for you to
customize as you wish.
It is recommended that these customized functions be allocated in a named section
that begins with .lib. This will cause the linker to allocate them near to the rest of the
library functions, which is where they ought to be.
The simplest way to redirect standard I/O to the peripheral of your choice is to select
one of the default handles already in use. Also, you could open files with a specific
name via fopen() by rewriting open() to return a new handle to be recognized by
read() or write() as appropriate.
If only a specific peripheral is required, then you could associate handle 1 == stdout
or 2 == stderr to another peripheral by writing the correct code to talk to the interested
peripheral.
A complete generic solution might be:
/* should be in a header file */
enum my_handles {
handle_stdin,
handle_stdout,
handle_stderr,
handle_can1,
handle_can2,
handle_spi1,
handle_spi2,
};
int __attribute__((__weak__, __section__(".libc")))
open(const char *name, int access, int mode) {
switch (name[0]) {
case 'i' : return handle_stdin;
case 'o' : return handle_stdout;
case 'e' : return handle_stderr;
case 'c' : return handle_can1;
case 'C' : return handle_can2;
case 's' : return handle_spi1;
case 'S' : return handle_spi2;
default: return handle_stderr;
}
}
Single letters were used in this example because they are faster to check and use less
memory. However, if memory is not an issue, you could use strcmp to compare full
names.
DS50001456J-page 48
 2004-2014 Microchip Technology Inc.
Standard C Libraries
In write(), you would write:
int __attribute__((__section__(".libc.write")))
write(int handle, void *buffer, unsigned int len) {
int i;
volatile UxMODEBITS *umode = &U1MODEbits;
volatile UxSTABITS *ustatus = &U1STAbits;
volatile unsigned int *txreg = &U1TXREG;
volatile unsigned int *brg = &U1BRG;
switch (handle)
{
default:
case 0:
case 1:
case 2:
if ((__C30_UART != 1) && (&U2BRG))
umode = &U2MODEbits;
ustatus = &U2STAbits;
txreg = &U2TXREG;
brg = &U2BRG;
}
if ((umode->UARTEN) == 0)
{
*brg = 0;
umode->UARTEN = 1;
}
if ((ustatus->UTXEN) == 0)
{
ustatus->UTXEN = 1;
}
for (i = len; i; --i)
{
while ((ustatus->TRMT) ==0);
*txreg = *(char*)buffer++;
}
break;
case handle_can1: /* code to support
break;
case handle_can2: /* code to support
break;
case handle_spi1: /* code to support
break;
case handle_spi2: /* code to support
break;
}
return(len);
{
can1 */
can2 */
spi1 */
spi2 */
}
where you would fill in the appropriate code as specified in the comments.
Now you can use the generic C STDIO features to write to another port:
FILE *can1 = fopen("c","w");
fprintf(can1,"This will be output through the can\n");
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16-Bit Language Tools Libraries
2.13.3
STDIO Functions
FILE
Description:
Stores information for a file stream.
Include:
<stdio.h>
fpos_t
Description:
Type of a variable used to store a file position.
Include:
<stdio.h>
size_t
Description:
The result type of the sizeof operator.
Include:
<stdio.h>
_IOFBF
Description:
Indicates full buffering.
Include:
<stdio.h>
Remarks:
Used by the function, setvbuf.
_IOLBF
Description:
Indicates line buffering.
Include:
<stdio.h>
Remarks:
Used by the function, setvbuf.
_IONBF
Description:
Indicates no buffering.
Include:
<stdio.h>
Remarks:
Used by the function, setvbuf.
BUFSIZ
Description:
Defines the size of the buffer used by the function setbuf.
Include:
<stdio.h>
Value:
512
EOF
DS50001456J-page 50
Description:
A negative number indicating the end-of-file has been reached or to
report an error condition.
Include:
<stdio.h>
Remarks:
If an end-of-file is encountered, the end-of-file indicator is set. If an
error condition is encountered, the error indicator is set. Error
conditions include write errors and input or read errors.
 2004-2014 Microchip Technology Inc.
Standard C Libraries
FILENAME_MAX
Description:
Maximum number of characters in a filename including the null
terminator.
Include:
<stdio.h>
Value:
260
FOPEN_MAX
Description:
Defines the maximum number of files that can be simultaneously open.
Include:
<stdio.h>
Value:
8
Remarks:
stderr, stdin and stdout are included in the FOPEN_MAX count.
L_tmpnam
Description:
Defines the number of characters for the longest temporary filename
created by the function tmpnam.
Include:
<stdio.h>
Value:
16
Remarks:
L_tmpnam is used to define the size of the array used by tmpnam.
NULL
Description:
The value of a null pointer constant.
Include:
<stdio.h>
SEEK_CUR
Description:
Indicates that fseek should seek from the current position of the file
pointer.
Include:
<stdio.h>
Example:
See example for fseek.
SEEK_END
Description:
Indicates that fseek should seek from the end of the file.
Include:
<stdio.h>
Example:
See example for fseek.
SEEK_SET
Description:
Indicates that fseek should seek from the beginning of the file.
Include:
<stdio.h>
Example:
See example for fseek.
stderr
Description:
File pointer to the standard error stream.
Include:
<stdio.h>
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stdin
Description:
File pointer to the standard input stream.
Include:
<stdio.h>
stdout
Description:
File pointer to the standard output stream.
Include:
<stdio.h>
TMP_MAX
DS50001456J-page 52
Description:
The maximum number of unique filenames the function tmpnam can
generate.
Include:
<stdio.h>
Value:
32
 2004-2014 Microchip Technology Inc.
Standard C Libraries
clearerr
Description:
Resets the error indicator for the stream.
Include:
<stdio.h>
Prototype:
void clearerr(FILE *stream);
Argument:
stream
Remarks:
The function clears the end-of-file and error indicators for the given
stream (i.e., feof and ferror will return false after the function
clearerr is called).
stream to reset error indicators
Example:
/* This program tries to write to a file that is
/* readonly. This causes the error indicator to
/* be set. The function ferror is used to check
/* the error indicator. The function clearerr is
/* used to reset the error indicator so the next
/* time ferror is called it will not report an
/* error.
#include <stdio.h> /* for ferror, clearerr, */
/* printf, fprintf, fopen,*/
/* fclose, FILE, NULL
*/
*/
*/
*/
*/
*/
*/
*/
int main(void)
{
FILE *myfile;
if ((myfile = fopen("sampclearerr.c", "r")) ==
NULL)
printf("Cannot open file\n");
else
{
fprintf(myfile, "Write this line to the "
"file.\n");
if (ferror(myfile))
printf("Error\n");
else
printf("No error\n");
clearerr(myfile);
if (ferror(myfile))
printf("Still has Error\n");
else
printf("Error indicator reset\n");
fclose(myfile);
}
}
Output:
Error
Error indicator reset
 2004-2014 Microchip Technology Inc.
DS50001456J-page 53
16-Bit Language Tools Libraries
fclose
Description:
Close a stream.
Include:
<stdio.h>
Prototype:
int fclose(FILE *stream);
Argument:
stream
Return Value:
Returns 0 if successful; otherwise, returns EOF if any errors were
detected.
Remarks:
fclose writes any buffered output to the file.
This function requires a heap.
Example:
#include <stdio.h> /* for fopen, fclose,
*/
/* printf,FILE, NULL, EOF */
pointer to the stream to close
int main(void)
{
FILE *myfile1, *myfile2;
int y;
if ((myfile1 = fopen("afile1", "w+")) == NULL)
printf("Cannot open afile1\n");
else
{
printf("afile1 was opened\n");
y = fclose(myfile1);
if (y == EOF)
printf("afile1 was not closed\n");
else
printf("afile1 was closed\n");
}
}
Output:
afile1 was opened
afile1 was closed
DS50001456J-page 54
 2004-2014 Microchip Technology Inc.
Standard C Libraries
fdopen
Description:
Associate a stream with a file descriptor.
Include:
<stdio.h>
Prototype:
FILE *fdopen(int fildes, const char *mode);
Arguments:
fildes
file descriptor
mode
type of access permitted
Return Value:
Returns a pointer to the open stream. If the function fails, a null pointer
is returned.
Remarks:
The following are types of file access:
r-
opens an existing text file for reading
w-
opens an empty text file for writing.
a-
opens a text file for appending.
rb -
opens an existing binary file for reading.
wb -
opens an empty binary file for writing.
ab -
opens a binary file for appending.
r+ -
opens an existing text file for reading and writing.
w+ -
opens an empty text file for reading and writing.
a+ -
opens a text file for reading and appending.
r+b or rb+ -
opens an existing binary file for reading and writing.
w+b or wb+ -
opens an empty binary file for reading and writing.
a+b or ab+ -
opens a binary file for reading and appending.
This function requires a heap.
Example:
#include <stdio.h> /* for fdopen, fclose, */
/* printf, FILE,
*/
/* NULL, EOF
*/
int main(void)
{
FILE *myfile1, *myfile2;
int y;
 2004-2014 Microchip Technology Inc.
DS50001456J-page 55
16-Bit Language Tools Libraries
fdopen (Continued)
if ((myfile1 = fdopen("afile1", "r")) == NULL)
printf("Cannot open afile1\n");
else
{
printf("afile1 was opened\n");
y = fclose(myfile1);
if (y == EOF)
printf("afile1 was not closed\n");
else
printf("afile1 was closed\n");
}
if ((myfile1 = fdopen("afile1", "w+")) == NULL)
printf("Second try, cannot open afile1\n");
else
{
printf("Second try, afile1 was opened\n");
y = fclose(myfile1);
if (y == EOF)
printf("afile1 was not closed\n");
else
printf("afile1 was closed\n");
}
if ((myfile2 = fdopen("afile2", "a+")) == NULL)
printf("Cannot open afile2\n");
else
{
printf("afile2 was opened\n");
y = fclose(myfile2);
if (y == EOF)
printf("afile2 was not closed\n");
else
printf("afile2 was closed\n");
}
}
Output:
Cannot
Second
afile1
Cannot
open afile1
try, afile1 was opened
was closed
open afile2
Explanation:
afile1 must exist before it can be opened for reading (r) or the
fdopen function will fail.
If the fdopen function opens a file for writing (w+) that doesn’t exist, it
will be created and then opened. If the file does exist, it cannot be overwritten and will be appended.
If the fdopen function attempts to append a file (a+) that doesn’t exist,
it will NOT be created and fdopen will fail. If the file does exist, it will
be opened for appending.
DS50001456J-page 56
 2004-2014 Microchip Technology Inc.
Standard C Libraries
feof
Description:
Tests for end-of-file.
Include:
<stdio.h>
Prototype:
int feof(FILE *stream);
Argument:
stream
Return Value:
Returns non-zero if stream is at the end-of-file; otherwise, returns zero.
Example:
#include <stdio.h> /* for feof, fgetc, fputc, */
/* fopen, fclose, FILE,
*/
/* NULL */
stream to check for end-of-file
int main(void)
{
FILE *myfile;
int y = 0;
if( (myfile = fopen( "afile.txt", "rb" )) == NULL )
printf( "Cannot open file\n" );
else
{
for (;;)
{
y = fgetc(myfile);
if (feof(myfile))
break;
fputc(y, stdout);
}
fclose( myfile );
}
}
Input:
Contents of afile.txt (used as input):
This is a sentence.
Output:
This is a sentence.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 57
16-Bit Language Tools Libraries
ferror
Description:
Tests if error indicator is set.
Include:
<stdio.h>
Prototype:
int ferror(FILE *stream);
Argument:
stream
Return Value:
Returns a non-zero value if error indicator is set; otherwise, returns a
zero.
Example:
/*
/*
/*
/*
/*
/*
/*
pointer to FILE structure
This program tries to write to a file that is
readonly. This causes the error indicator to
be set. The function ferror is used to check
the error indicator and find the error. The
function clearerr is used to reset the error
indicator so the next time ferror is called
it will not report an error.
#include <stdio.h> /*
/*
/*
/*
for ferror, clearerr,
printf, fprintf,
fopen, fclose,
FILE, NULL
*/
*/
*/
*/
*/
*/
*/
*/
*/
*/
*/
int main(void)
{
FILE *myfile;
if ((myfile = fopen("sampclearerr.c", "r")) ==
NULL)
printf("Cannot open file\n");
else
{
fprintf(myfile, "Write this line to the "
"file.\n");
if (ferror(myfile))
printf("Error\n");
else
printf("No error\n");
clearerr(myfile);
if (ferror(myfile))
printf("Still has Error\n");
else
printf("Error indicator reset\n");
fclose(myfile);
}
}
Output:
Error
Error indicator reset
DS50001456J-page 58
 2004-2014 Microchip Technology Inc.
Standard C Libraries
fflush
Description:
Flushes the buffer in the specified stream.
Include:
<stdio.h>
Prototype:
int fflush(FILE *stream);
Argument:
stream
Return Value:
Returns EOF if a write error occurs; otherwise, returns zero for success.
Remarks:
If stream is a null pointer, all output buffers are written to files. fflush
has no effect on an unbuffered stream.
pointer to the stream to flush.
fgetc
Description:
Get a character from a stream
Include:
<stdio.h>
Prototype:
int fgetc(FILE *stream);
Argument:
stream
Return Value:
Returns the character read or EOF if a read error occurs or end-of-file
is reached.
Remarks:
The function reads the next character from the input stream, advances
the file-position indicator and returns the character as an unsigned
char converted to an int.
Example:
#include <stdio.h> /* for fgetc, printf, */
/* fclose, FILE,
*/
/* NULL, EOF
*/
pointer to the open stream
int main(void)
{
FILE *buf;
char y;
if ((buf = fopen("afile.txt", "r")) == NULL)
printf("Cannot open afile.txt\n");
else
{
y = fgetc(buf);
while (y != EOF)
{
printf("%c|", y);
y = fgetc(buf);
}
fclose(buf);
}
}
Input:
Contents of afile.txt (used as input):
Short
Longer string
Output:
S|h|o|r|t|
|L|o|n|g|e|r| |s|t|r|i|n|g|
|
 2004-2014 Microchip Technology Inc.
DS50001456J-page 59
16-Bit Language Tools Libraries
fgetpos
Description:
Gets the stream’s file position.
Include:
<stdio.h>
Prototype:
int fgetpos(FILE *stream, fpos_t *pos);
Arguments:
stream
target stream
pos
position-indicator storage
Return Value:
Returns 0 if successful; otherwise, returns a non-zero value.
Remarks:
The function stores the file-position indicator for the given stream in
*pos if successful, otherwise, fgetpos sets errno.
Example:
/*
/*
/*
/*
/*
/*
/*
This program opens a file and reads bytes at */
several different locations. The fgetpos
*/
function notes the 8th byte. 21 bytes are
*/
read then 18 bytes are read. Next the
*/
fsetpos function is set based on the
*/
fgetpos position and the previous 21 bytes
*/
are reread.
*/
#include <stdio.h> /*
/*
/*
/*
for fgetpos, fread,
printf, fopen, fclose,
FILE, NULL, perror,
fpos_t, sizeof
*/
*/
*/
*/
int main(void)
{
FILE
*myfile;
fpos_t pos;
char
buf[25];
if ((myfile = fopen("sampfgetpos.c", "rb")) ==
NULL)
printf("Cannot open file\n");
else
{
fread(buf, sizeof(char), 8, myfile);
if (fgetpos(myfile, &pos) != 0)
perror("fgetpos error");
else
{
fread(buf, sizeof(char), 21, myfile);
printf("Bytes read: %.21s\n", buf);
fread(buf, sizeof(char), 18, myfile);
printf("Bytes read: %.18s\n", buf);
}
if (fsetpos(myfile, &pos) != 0)
perror("fsetpos error");
fread(buf, sizeof(char), 21, myfile);
printf("Bytes read: %.21s\n", buf);
fclose(myfile);
}
}
Output:
Bytes read: program opens a file
Bytes read: and reads bytes at
Bytes read: program opens a file
DS50001456J-page 60
 2004-2014 Microchip Technology Inc.
Standard C Libraries
fgets
Description:
Get a string from a stream.
Include:
<stdio.h>
Prototype:
char *fgets(char *s, int n, FILE *stream);
Arguments:
s
pointer to the storage string
n
maximum number of characters to read
stream
pointer to the open stream.
Return Value:
Returns a pointer to the string s if successful; otherwise, returns a null
pointer.
Remarks:
The function reads characters from the input stream and stores them
into the string pointed to by s until it has read n-1 characters, stores a
newline character or sets the end-of-file or error indicators. If any characters were stored, a null character is stored immediately after the last
read character in the next element of the array. If fgets sets the error
indicator, the array contents are indeterminate.
Example:
#include <stdio.h> /* for fgets, printf, */
/* fopen, fclose,
*/
/* FILE, NULL
*/
#define MAX 50
int main(void)
{
FILE *buf;
char s[MAX];
if ((buf = fopen("afile.txt", "r")) == NULL)
printf("Cannot open afile.txt\n");
else
{
while (fgets(s, MAX, buf) != NULL)
{
printf("%s|", s);
}
fclose(buf);
}
}
Input:
Contents of afile.txt (used as input):
Short
Longer string
Output:
Short
|Longer string
|
 2004-2014 Microchip Technology Inc.
DS50001456J-page 61
16-Bit Language Tools Libraries
fopen
Description:
Opens a file.
Include:
<stdio.h>
Prototype:
FILE *fopen(const char *filename, const char *mode);
Arguments:
filename
name of the file
mode
type of access permitted
Return Value:
Returns a pointer to the open stream. If the function fails a null pointer
is returned.
Remarks:
The following are types of file access:
r-
opens an existing text file for reading
wopens an empty text file for writing. (An existing file will
be overwritten).
aopens a text file for appending. (A file is created if it
doesn’t exist).
rb -
opens an existing binary file for reading.
wb opens an empty binary file for writing. (An existing file
will be overwritten).
ab opens a binary file for appending. (A file is created if it
doesn’t exist).
r+ -
opens an existing text file for reading and writing.
w+ opens an empty text file for reading and writing. (An
existing file will be overwritten).
a+ opens a text file for reading and appending. (A file is
created if it doesn’t exist).
r+b or rb+ -
opens an existing binary file for reading and writing.
w+b or wb+ - opens an empty binary file for reading and writing. (An
existing file will be overwritten).
a+b or ab+ - opens a binary file for reading and appending. (A file is
created if it doesn’t exist).
This function requires a heap.
Example:
#include <stdio.h> /* for fopen, fclose, */
/* printf, FILE,
*/
/* NULL, EOF
*/
int main(void)
{
FILE *myfile1, *myfile2;
int y;
DS50001456J-page 62
 2004-2014 Microchip Technology Inc.
Standard C Libraries
fopen (Continued)
if ((myfile1 = fopen("afile1", "r")) == NULL)
printf("Cannot open afile1\n");
else
{
printf("afile1 was opened\n");
y = fclose(myfile1);
if (y == EOF)
printf("afile1 was not closed\n");
else
printf("afile1 was closed\n");
}
if ((myfile1 = fopen("afile1", "w+")) == NULL)
printf("Second try, cannot open afile1\n");
else
{
printf("Second try, afile1 was opened\n");
y = fclose(myfile1);
if (y == EOF)
printf("afile1 was not closed\n");
else
printf("afile1 was closed\n");
}
if ((myfile2 = fopen("afile2", "w+")) == NULL)
printf("Cannot open afile2\n");
else
{
printf("afile2 was opened\n");
y = fclose(myfile2);
if (y == EOF)
printf("afile2 was not closed\n");
else
printf("afile2 was closed\n");
}
}
Output:
Cannot
Second
afile1
afile2
afile2
open afile1
try, afile1 was opened
was closed
was opened
was closed
Explanation:
afile1 must exist before it can be opened for reading (r) or the
fopen function will fail. If the fopen function opens a file for writing
(w+) it does not have to already exist. If it doesn’t exist, it will be created
and then opened.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 63
16-Bit Language Tools Libraries
fprintf
Description:
Prints formatted data to a stream.
Include:
<stdio.h>
Prototype:
int fprintf(FILE *stream, const char *format, ...);
Arguments:
stream
pointer to the stream in which to output data
format
format control string
...
optional arguments
Return Value:
Returns number of characters generated or a negative number if an
error occurs.
Remarks:
The format argument has the same syntax and use that it has in
print.
Example:
#include <stdio.h> /* for fopen, fclose, */
/* fprintf, printf,
*/
/* FILE, NULL
*/
int main(void)
{
FILE *myfile;
int y;
char s[]="Print this string";
int x = 1;
char a = '\n';
if ((myfile = fopen("afile", "w")) == NULL)
printf("Cannot open afile\n");
else
{
y = fprintf(myfile, "%s %d time%c", s, x, a);
printf("Number of characters printed "
"to file = %d",y);
fclose(myfile);
}
}
Output:
Number of characters printed to file = 25
Contents of afile:
Print this string 1 time
DS50001456J-page 64
 2004-2014 Microchip Technology Inc.
Standard C Libraries
fputc
Description:
Puts a character to the stream.
Include:
<stdio.h>
Prototype:
int fputc(int c, FILE *stream);
Arguments:
c
character to be written
stream
pointer to the open stream
Return Value:
Returns the character written or EOF if a write error occurs.
Remarks:
The function writes the character to the output stream, advances the
file-position indicator and returns the character as an unsigned char
converted to an int.
Example:
#include <stdio.h> /* for fputc, EOF, stdout */
int main(void)
{
char *y;
char buf[] = "This is text\n";
int x;
x = 0;
for (y = buf; (x != EOF) && (*y != '\0'); y++)
{
x = fputc(*y, stdout);
fputc('|', stdout);
}
}
Output:
T|h|i|s| |i|s| |t|e|x|t|
|
fputs
Description:
Puts a string to the stream.
Include:
<stdio.h>
Prototype:
int fputs(const char *s, FILE *stream);
Arguments:
s
string to be written
stream
pointer to the open stream
Return Value:
Returns a non-negative value if successful; otherwise, returns EOF.
Remarks:
The function writes characters to the output stream up to but not
including the null character.
Example:
#include <stdio.h> /* for fputs, stdout */
int main(void)
{
char buf[] = "This is text\n";
fputs(buf,stdout);
fputs("|",stdout);
}
Output:
This is text
|
 2004-2014 Microchip Technology Inc.
DS50001456J-page 65
16-Bit Language Tools Libraries
fread
Description:
Reads data from the stream.
Include:
<stdio.h>
Prototype:
size_t fread(void *ptr, size_t size, size_t nelem,
FILE *stream);
Arguments:
ptr
pointer to the storage buffer
size
size of item
nelem
maximum number of items to be read
stream
pointer to the stream
Return Value:
Returns the number of complete elements read up to nelem whose
size is specified by size.
Remarks:
The function reads characters from a given stream into the buffer
pointed to by ptr until the function stores size * nelem characters
or sets the end-of-file or error indicator. fread returns n/size where n is
the number of characters it read. If n is not a multiple of size, the value
of the last element is indeterminate. If the function sets the error
indicator, the file-position indicator is indeterminate.
Example:
#include <stdio.h> /* for fread, fwrite,
*/
/* printf, fopen, fclose, */
/* sizeof, FILE, NULL
*/
int main(void)
{
FILE *buf;
int x, numwrote, numread;
double nums[10], readnums[10];
if ((buf = fopen("afile.out", "w+")) != NULL)
{
for (x = 0; x < 10; x++)
{
nums[x] = 10.0/(x + 1);
printf("10.0/%d = %f\n", x+1, nums[x]);
}
numwrote = fwrite(nums, sizeof(double),
10, buf);
printf("Wrote %d numbers\n\n", numwrote);
fclose(buf);
}
else
printf("Cannot open afile.out\n");
DS50001456J-page 66
 2004-2014 Microchip Technology Inc.
Standard C Libraries
fread (Continued)
if ((buf = fopen("afile.out", "r+")) != NULL)
{
numread = fread(readnums, sizeof(double),
10, buf);
printf("Read %d numbers\n", numread);
for (x = 0; x < 10; x++)
{
printf("%d * %f = %f\n", x+1, readnums[x],
(x + 1) * readnums[x]);
}
fclose(buf);
}
else
printf("Cannot open afile.out\n");
}
Output:
10.0/1 = 10.000000
10.0/2 = 5.000000
10.0/3 = 3.333333
10.0/4 = 2.500000
10.0/5 = 2.000000
10.0/6 = 1.666667
10.0/7 = 1.428571
10.0/8 = 1.250000
10.0/9 = 1.111111
10.0/10 = 1.000000
Wrote 10 numbers
Read 10 numbers
1 * 10.000000 = 10.000000
2 * 5.000000 = 10.000000
3 * 3.333333 = 10.000000
4 * 2.500000 = 10.000000
5 * 2.000000 = 10.000000
6 * 1.666667 = 10.000000
7 * 1.428571 = 10.000000
8 * 1.250000 = 10.000000
9 * 1.111111 = 10.000000
10 * 1.000000 = 10.000000
Explanation:
This program uses fwrite to save 10 numbers to a file in binary form.
This allows the numbers to be saved in the same pattern of bits as the
program is using, which provides more accuracy and consistency.
Using fprintf would save the numbers as text strings, which could
cause the numbers to be truncated. Each number is divided into 10 to
produce a variety of numbers. Retrieving the numbers with fread to a
new array and multiplying them by the original number shows the
numbers were not truncated in the save process.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 67
16-Bit Language Tools Libraries
freopen
Description:
Reassigns an existing stream to a new file.
Include:
<stdio.h>
Prototype:
FILE *freopen(const char *filename, const char
*mode, FILE *stream);
Arguments:
filename
name of the new file
mode
type of access permitted
stream
pointer to the currently open stream
Return Value:
Returns a pointer to the new open file. If the function fails a null pointer
is returned.
Remarks:
The function closes the file associated with the stream as though
fclose was called. Then it opens the new file as though fopen was
called. freopen will fail if the specified stream is not open. See fopen
for the possible types of file access.
This function requires a heap.
Example:
#include <stdio.h> /* for fopen, freopen, */
/* printf, fclose,
*/
/* FILE, NULL
*/
int main(void)
{
FILE *myfile1, *myfile2;
int y;
if ((myfile1 = fopen("afile1", "w+")) == NULL)
printf("Cannot open afile1\n");
else
{
printf("afile1 was opened\n");
if ((myfile2 = freopen("afile2", "w+",
myfile1)) == NULL)
{
printf("Cannot open afile2\n");
fclose(myfile1);
}
else
{
printf("afile2 was opened\n");
fclose(myfile2);
}
}
}
Output:
afile1 was opened
afile2 was opened
Explanation:
This program uses myfile2 to point to the stream when freopen is
called, so if an error occurs, myfile1 will still point to the stream and
can be closed properly. If the freopen call is successful, myfile2 can
be used to close the stream properly.
fscanf
Description:
DS50001456J-page 68
Scans formatted text from a stream.
 2004-2014 Microchip Technology Inc.
Standard C Libraries
fscanf (Continued)
Include:
<stdio.h>
Prototype:
int fscanf(FILE *stream, const char *format, ...);
Arguments:
stream
pointer to the open stream from which to read data
format
format control string
...
optional arguments
Return Value:
Returns the number of items successfully converted and assigned. If
no items are assigned, a 0 is returned. EOF is returned if end-of-file is
encountered before the first conversion or if an error occurs.
Remarks:
The format argument has the same syntax and use that it has in
scanf.
Example:
#include <stdio.h> /*
/*
/*
/*
for fopen, fscanf,
fclose, fprintf,
fseek, printf, FILE,
NULL, SEEK_SET
*/
*/
*/
*/
int main(void)
{
FILE *myfile;
char s[30];
int x;
char a;
if ((myfile = fopen("afile", "w+")) == NULL)
printf("Cannot open afile\n");
else
{
fprintf(myfile, "%s %d times%c",
"Print this string", 100, '\n');
fseek(myfile, 0L, SEEK_SET);
fscanf(myfile,
printf("%s\n",
fscanf(myfile,
printf("%s\n",
fscanf(myfile,
printf("%s\n",
fscanf(myfile,
printf("%d\n",
fscanf(myfile,
printf("%s\n",
fscanf(myfile,
printf("%c\n",
"%s",
s);
"%s",
s);
"%s",
s);
"%d",
x);
"%s",
s);
"%c",
a);
s);
s);
s);
&x);
s);
a);
fclose(myfile);
}
}
Input:
Contents of afile:
Print this string 100 times
 2004-2014 Microchip Technology Inc.
DS50001456J-page 69
16-Bit Language Tools Libraries
fscanf (Continued)
Output:
Print
this
string
100
times
fseek
Description:
Moves file pointer to a specific location.
Include:
<stdio.h>
Prototype:
int fseek(FILE *stream, long offset, int mode);
Arguments:
stream
stream in which to move the file pointer.
offset
value to add to the current position
mode
type of seek to perform
Return Value:
Returns 0 if successful; otherwise, returns a non-zero value and set
errno.
Remarks:
mode can be one of the following:
SEEK_SET – seeks from the beginning of the file
SEEK_CUR – seeks from the current position of the file pointer
SEEK_END – seeks from the end of the file
Example:
#include <stdio.h> /*
/*
/*
/*
/*
for fseek, fgets,
printf, fopen, fclose,
FILE, NULL, perror,
SEEK_SET, SEEK_CUR,
SEEK_END
*/
*/
*/
*/
*/
int main(void)
{
FILE *myfile;
char s[70];
int y;
myfile = fopen("afile.out", "w+");
if (myfile == NULL)
printf("Cannot open afile.out\n");
else
{
fprintf(myfile, "This is the beginning, "
"this is the middle and "
"this is the end.");
y = fseek(myfile, 0L, SEEK_SET);
if (y)
perror("Fseek failed");
else
{
fgets(s, 22, myfile);
printf("\"%s\"\n\n", s);
}
DS50001456J-page 70
 2004-2014 Microchip Technology Inc.
Standard C Libraries
fseek (Continued)
y = fseek(myfile, 2L, SEEK_CUR);
if (y)
perror("Fseek failed");
else
{
fgets(s, 70, myfile);
printf("\"%s\"\n\n", s);
}
y = fseek(myfile, -16L, SEEK_END);
if (y)
perror("Fseek failed");
else
{
fgets(s, 70, myfile);
printf("\"%s\"\n", s);
}
fclose(myfile);
}
}
Output:
"This is the beginning"
"this is the middle and this is the end."
"this is the end."
Explanation:
The file afile.out is created with the text, “This is the beginning, this
is the middle and this is the end”.
The function fseek uses an offset of zero and SEEK_SET to set the file
pointer to the beginning of the file. fgets then reads 22 characters
which are “This is the beginning”, and adds a null character to the
string.
Next, fseek uses an offset of two and SEEK_CURRENT to set the file
pointer to the current position plus two (skipping the comma and
space). fgets then reads up to the next 70 characters. The first 39
characters are “this is the middle and this is the end”. It stops when it
reads EOF and adds a null character to the string.
Finally, fseek uses an offset of negative 16 characters and SEEK_END
to set the file pointer to 16 characters from the end of the file. fgets
then reads up to 70 characters. It stops at the EOF after reading
16 characters “this is the end”, and adds a null character to the string.
fsetpos
Description:
Sets the stream’s file position.
Include:
<stdio.h>
Prototype:
int fsetpos(FILE *stream, const fpos_t *pos);
Arguments:
stream
target stream
pos
to fgetpos
position-indicator storage as returned by an earlier call
Return Value:
Returns 0 if successful; otherwise, returns a non-zero value.
Remarks:
The function sets the file-position indicator for the given stream in *pos
if successful; otherwise, fsetpos sets errno.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 71
16-Bit Language Tools Libraries
fsetpos (Continued)
Example:
/*
/*
/*
/*
/*
/*
/*
This program opens a file and reads bytes at */
several different locations. The fgetpos
*/
function notes the 8th byte. 21 bytes are
*/
read then 18 bytes are read. Next, the
*/
fsetpos function is set based on the
*/
fgetpos position and the previous 21 bytes
*/
are reread.
*/
#include <stdio.h> /*
/*
/*
/*
for fgetpos, fread,
printf, fopen, fclose,
FILE, NULL, perror,
fpos_t, sizeof
*/
*/
*/
*/
int main(void)
{
FILE
*myfile;
fpos_t pos;
char
buf[25];
if ((myfile = fopen("sampfgetpos.c", "rb")) ==
NULL)
printf("Cannot open file\n");
else
{
fread(buf, sizeof(char), 8, myfile);
if (fgetpos(myfile, &pos) != 0)
perror("fgetpos error");
else
{
fread(buf, sizeof(char), 21, myfile);
printf("Bytes read: %.21s\n", buf);
fread(buf, sizeof(char), 18, myfile);
printf("Bytes read: %.18s\n", buf);
}
if (fsetpos(myfile, &pos) != 0)
perror("fsetpos error");
fread(buf, sizeof(char), 21, myfile);
printf("Bytes read: %.21s\n", buf);
fclose(myfile);
}
}
Output:
Bytes read: program opens a file
Bytes read: and reads bytes at
Bytes read: program opens a file
DS50001456J-page 72
 2004-2014 Microchip Technology Inc.
Standard C Libraries
ftell
Description:
Gets the current position of a file pointer.
Include:
<stdio.h>
Prototype:
long ftell(FILE *stream);
Argument:
stream
Return Value:
Returns the position of the file pointer if successful; otherwise, returns
-1.
Example:
#include <stdio.h> /*
/*
/*
/*
stream in which to get the current file position
for ftell, fread,
*/
fprintf, printf,
*/
fopen, fclose, sizeof, */
FILE, NULL */
int main(void)
{
FILE *myfile;
char s[75];
long y;
myfile = fopen("afile.out", "w+");
if (myfile == NULL)
printf("Cannot open afile.out\n");
else
{
fprintf(myfile,"This is a very long sentence "
"for input into the file named "
"afile.out for testing.");
fclose(myfile);
if ((myfile = fopen("afile.out", "rb")) != NULL)
{
printf("Read some characters:\n");
fread(s, sizeof(char), 29, myfile);
printf("\t\"%s\"\n", s);
y = ftell(myfile);
printf("The current position of the "
"file pointer is %ld\n", y);
fclose(myfile);
}
}
}
Output:
Read some characters:
"This is a very long sentence "
The current position of the file pointer is 29
 2004-2014 Microchip Technology Inc.
DS50001456J-page 73
16-Bit Language Tools Libraries
fwrite
Description:
Writes data to the stream.
Include:
<stdio.h>
Prototype:
size_t fwrite(const void *ptr, size_t size,
size_t nelem, FILE *stream);
Arguments:
ptr
pointer to the storage buffer
size
size of item
nelem
maximum number of items to be read
stream
pointer to the open stream
Return Value:
Returns the number of complete elements successfully written, which
will be less than nelem only if a write error is encountered.
Remarks:
The function writes characters to a given stream from a buffer pointed
to by ptr up to nelem elements whose size is specified by size. The
file position indicator is advanced by the number of characters successfully written. If the function sets the error indicator, the file-position
indicator is indeterminate.
Example:
#include <stdio.h> /* for fread, fwrite,
*/
/* printf, fopen, fclose, */
/* sizeof, FILE, NULL
*/
int main(void)
{
FILE *buf;
int x, numwrote, numread;
double nums[10], readnums[10];
if ((buf = fopen("afile.out", "w+")) != NULL)
{
for (x = 0; x < 10; x++)
{
nums[x] = 10.0/(x + 1);
printf("10.0/%d = %f\n", x+1, nums[x]);
}
numwrote = fwrite(nums, sizeof(double),
10, buf);
printf("Wrote %d numbers\n\n", numwrote);
fclose(buf);
}
else
printf("Cannot open afile.out\n");
DS50001456J-page 74
 2004-2014 Microchip Technology Inc.
Standard C Libraries
fwrite (Continued)
if ((buf = fopen("afile.out", "r+")) != NULL)
{
numread = fread(readnums, sizeof(double),
10, buf);
printf("Read %d numbers\n", numread);
for (x = 0; x < 10; x++)
{
printf("%d * %f = %f\n", x+1, readnums[x],
(x + 1) * readnums[x]);
}
fclose(buf);
}
else
printf("Cannot open afile.out\n");
}
Output:
10.0/1 = 10.000000
10.0/2 = 5.000000
10.0/3 = 3.333333
10.0/4 = 2.500000
10.0/5 = 2.000000
10.0/6 = 1.666667
10.0/7 = 1.428571
10.0/8 = 1.250000
10.0/9 = 1.111111
10.0/10 = 1.000000
Wrote 10 numbers
Read 10 numbers
1 * 10.000000 = 10.000000
2 * 5.000000 = 10.000000
3 * 3.333333 = 10.000000
4 * 2.500000 = 10.000000
5 * 2.000000 = 10.000000
6 * 1.666667 = 10.000000
7 * 1.428571 = 10.000000
8 * 1.250000 = 10.000000
9 * 1.111111 = 10.000000
10 * 1.000000 = 10.000000
Explanation:
This program uses fwrite to save 10 numbers to a file in binary form.
This allows the numbers to be saved in the same pattern of bits as the
program is using which provides more accuracy and consistency. Using
fprintf would save the numbers as text strings, which could cause
the numbers to be truncated. Each number is divided into 10 to produce a variety of numbers. Retrieving the numbers with fread to a
new array and multiplying them by the original number shows the
numbers were not truncated in the save process.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 75
16-Bit Language Tools Libraries
getc
Description:
Get a character from the stream.
Include:
<stdio.h>
Prototype:
int getc(FILE *stream);
Argument:
stream
Return Value:
Returns the character read or EOF if a read error occurs or end-of-file
is reached.
Remarks:
getc is the same as the function fgetc.
Example:
#include <stdio.h> /* for getc, printf, */
/* fopen, fclose,
*/
/* FILE, NULL, EOF
*/
pointer to the open stream
int main(void)
{
FILE *buf;
char y;
if ((buf = fopen("afile.txt", "r")) == NULL)
printf("Cannot open afile.txt\n");
else
{
y = getc(buf);
while (y != EOF)
{
printf("%c|", y);
y = getc(buf);
}
fclose(buf);
}
}
Input:
Contents of afile.txt (used as input):
Short
Longer string
Output:
S|h|o|r|t|
|L|o|n|g|e|r| |s|t|r|i|n|g|
|
DS50001456J-page 76
 2004-2014 Microchip Technology Inc.
Standard C Libraries
getchar
Description:
Get a character from stdin.
Include:
<stdio.h>
Prototype:
int getchar(void);
Return Value:
Returns the character read or EOF if a read error occurs or end-of-file
is reached.
Remarks:
Same effect as fgetc with the argument stdin.
Example:
#include <stdio.h> /* for getchar, printf */
int main(void)
{
char y;
y = getchar();
printf("%c|", y);
y = getchar();
printf("%c|", y);
y = getchar();
printf("%c|", y);
y = getchar();
printf("%c|", y);
y = getchar();
printf("%c|", y);
}
Input:
Contents of UartIn.txt (used as stdin input for simulator):
Short
Longer string
Output:
S|h|o|r|t|
gets
Description:
Get a string from stdin.
Include:
<stdio.h>
Prototype:
char *gets(char *s);
Argument:
s
Return Value:
Returns a pointer to the string s if successful; otherwise, returns a null
pointer.
Remarks:
The function reads characters from the stream stdin and stores them
into the string pointed to by s until it reads a newline character (which is
not stored) or sets the end-of-file or error indicators. If any characters
were read, a null character is stored immediately after the last read
character in the next element of the array. If gets sets the error
indicator, the array contents are indeterminate.
 2004-2014 Microchip Technology Inc.
pointer to the storage string
DS50001456J-page 77
16-Bit Language Tools Libraries
gets (Continued)
Example:
#include <stdio.h> /* for gets, printf */
int main(void)
{
char y[50];
gets(y) ;
printf("Text: %s\n", y);
}
Input:
Contents of UartIn.txt (used as stdin input for simulator):
Short
Longer string
Output:
Text: Short
perror
Description:
Prints an error message to stderr.
Include:
<stdio.h>
Prototype:
void perror(const char *s);
Argument:
s
Return Value:
None.
Remarks:
The string s is printed followed by a colon and a space. Then, an error
message based on errno is printed followed by an newline.
Example:
#include <stdio.h> /* for perror, fopen, */
/* fclose, printf,
*/
/* FILE, NULL
*/
string to print
int main(void)
{
FILE *myfile;
if ((myfile = fopen("samp.fil", "r+")) == NULL)
perror("Cannot open samp.fil");
else
printf("Success opening samp.fil\n");
fclose(myfile);
}
Output:
Cannot open samp.fil:
DS50001456J-page 78
file open error
 2004-2014 Microchip Technology Inc.
Standard C Libraries
printf
Description:
Prints formatted text to stdout.
Include:
<stdio.h>
Prototype:
int printf(const char *format, ...);
Arguments:
format
format control string
...
optional arguments
Return Value:
Returns number of characters generated or a negative number if an
error occurs.
Remarks:
There must be exactly the same number of arguments as there are format specifiers. If the are less arguments than match the format specifiers, the output is undefined. If there are more arguments than match
the format specifiers, the remaining arguments are discarded. Each format specifier begins with a percent sign followed by optional fields and
a required type as shown here:
%[flags][width][.precision][size]type
flags
0
+
space
#
left justify the value within a given field width
Use 0 for the pad character instead of space (which is the
default)
generate a plus sign for positive signed values
generate a space or signed values that have neither a plus
nor a minus sign
to prefix 0 on an octal conversion, to prefix 0x or 0X on a
hexadecimal conversion, or to generate a decimal point and
fraction digits that are otherwise suppressed on a floating-point conversion
width
specify the number of characters to generate for the conversion. If the
asterisk (*) is used instead of a decimal number, the next argument
(which must be of type int) will be used for the field width. If the result
is less than the field width, pad characters will be used on the left to fill
the field. If the result is greater than the field width, the field is
expanded to accommodate the value without padding.
precision
The field width can be followed with dot (.) and a decimal integer representing the precision that specifies one of the following:
- minimum number of digits to generate on an integer conversion
- number of fraction digits to generate on an e, E, or f conversion
- maximum number of significant digits to generate on a g or G
conversion
- maximum number of characters to generate from a C string on an s
conversion
If the period appears without the integer, the integer is assumed to be
zero. If the asterisk (*) is used instead of a decimal number, the next
argument (which must be of type int) will be used for the precision.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 79
16-Bit Language Tools Libraries
printf (Continued)
size
h modifier –
h modifier –
l modifier –
l modifier –
l modifier –
l modifier –
ll modifier –
ll modifier –
L modifier –
type
d, i
o
u
x
X
e, E
f
g, G
c
s
p
n
%
used with type d, i, o, u, x, X; converts the value to a
short int or unsigned short int
used with n; specifies that the pointer points to a short
int
used with type d, i, o, u, x, X; converts the value to a
long int or unsigned long int
used with n; specifies that the pointer points to a long
int
used with c; specifies a wide character
used with type e, E, f, F, g, G; converts the value to a
double
used with type d, i, o, u, x, X; converts the value to a
long long int or unsigned long long int
used with n; specifies that the pointer points to a long
long int
used with e, E, f, g, G; converts the value to a long
double
signed int
unsigned int in octal
unsigned int in decimal
unsigned int in lowercase hexadecimal
unsigned int in uppercase hexadecimal
double in scientific notation
double decimal notation
double (takes the form of e, E or f as appropriate)
char - a single character
string
value of a pointer
the associated argument shall be an integer pointer into
which is placed the number of characters written so far.
No characters are printed.
A % character is printed
This function requires a heap.
Example:
#include <stdio.h> /* for printf */
int main(void)
{
DS50001456J-page 80
/* print a character right justified in a 3
/* character space.
printf("%3c\n", 'a');
*/
*/
/* print an integer, left justified (as
/* specified by the minus sign in the format
/* string) in a 4 character space. Print a
/* second integer that is right justified in
/* a 4 character space using the pipe (|) as
/* a separator between the integers.
printf("%-4d|%4d\n", -4, 4);
*/
*/
*/
*/
*/
*/
/* print a number converted to octal in 4
/* digits.
printf("%.4o\n", 10);
*/
*/
 2004-2014 Microchip Technology Inc.
Standard C Libraries
printf (Continued)
/* print a number converted to hexadecimal
/* format with a 0x prefix.
printf("%#x\n", 28);
*/
*/
/* print a float in scientific notation
printf("%E\n", 1.1e20);
*/
/* print a float with 2 fraction digits
printf("%.2f\n", -3.346);
*/
/* print a long float with %E, %e, or %f
/* whichever is the shortest version
printf("%Lg\n", .02L);
*/
*/
}
Output:
a
-4 |
4
0012
0x1c
1.100000E+20
-3.35
0.02
putc
Description:
Puts a character to the stream.
Include:
<stdio.h>
Prototype:
int putc(int c, FILE *stream);
Arguments:
c
character to be written
stream
pointer to FILE structure
Return Value:
Returns the character or EOF if an error occurs or end-of-file is
reached.
Remarks:
putc is the same as the function fputc.
Example:
#include <stdio.h> /* for putc, EOF, stdout */
int main(void)
{
char *y;
char buf[] = "This is text\n";
int x;
x = 0;
for (y = buf; (x != EOF) && (*y != '\0'); y++)
{
x = putc(*y, stdout);
putc('|', stdout);
}
}
Output:
T|h|i|s| |i|s| |t|e|x|t|
|
 2004-2014 Microchip Technology Inc.
DS50001456J-page 81
16-Bit Language Tools Libraries
putchar
Description:
Put a character to stdout.
Include:
<stdio.h>
Prototype:
int putchar(int c);
Argument:
c
Return Value:
Returns the character or EOF if an error occurs or end-of-file is
reached.
Remarks:
Same effect as fputc with stdout as an argument.
Example:
#include <stdio.h> /* for putchar, printf, */
/* EOF, stdout
*/
character to be written
int main(void)
{
char *y;
char buf[] = "This is text\n";
int x;
x = 0;
for (y = buf; (x != EOF) && (*y != '\0'); y++)
x = putchar(*y);
}
Output:
This is text
puts
Description:
Put a string to stdout.
Include:
<stdio.h>
Prototype:
int puts(const char *s);
Argument:
s
Return Value:
Returns a non-negative value if successful; otherwise, returns EOF.
Remarks:
The function writes characters to the stream stdout. A newline character is appended. The terminating null character is not written to the
stream.
Example:
#include <stdio.h> /* for puts */
string to be written
int main(void)
{
char buf[] = "This is text\n";
puts(buf);
puts("|");
}
Output:
This is text
|
DS50001456J-page 82
 2004-2014 Microchip Technology Inc.
Standard C Libraries
remove
Description:
Deletes the specified file.
Include:
<stdio.h>
Prototype:
int remove(const char *filename);
Argument:
filename
Return Value:
Returns 0 if successful; otherwise, returns -1.
Remarks:
If filename does not exist or is open, remove will fail.
Example:
#include <stdio.h> /* for remove, printf */
name of file to be deleted
int main(void)
{
if (remove("myfile.txt") != 0)
printf("Cannot remove file");
else
printf("File removed");
}
Output:
File removed
rename
Description:
Renames the specified file.
Include:
<stdio.h>
Prototype:
int rename(const char *old, const char *new);
Arguments:
old
pointer to the old name
new
pointer to the new name
Return Value:
Return 0 if successful; otherwise, returns a non-zero value.
Remarks:
The new name must not already exist in the current working directory,
the old name must exist in the current working directory.
Example:
#include <stdio.h> /* for rename, printf */
int main(void)
{
if (rename("myfile.txt","newfile.txt") != 0)
printf("Cannot rename file");
else
printf("File renamed");
}
Output:
File renamed
 2004-2014 Microchip Technology Inc.
DS50001456J-page 83
16-Bit Language Tools Libraries
rewind
Description:
Resets the file pointer to the beginning of the file.
Include:
<stdio.h>
Prototype:
void rewind(FILE *stream);
Argument:
stream
Remarks:
The function calls fseek(stream, 0L, SEEK_SET) and then clears
the error indicator for the given stream.
Example:
#include <stdio.h> /*
/*
/*
/*
stream to reset the file pointer
for rewind, fopen,
fscanf, fclose,
fprintf, printf,
FILE, NULL
*/
*/
*/
*/
int main(void)
{
FILE *myfile;
char s[] = "cookies";
int x = 10;
if ((myfile = fopen("afile", "w+")) == NULL)
printf("Cannot open afile\n");
else
{
fprintf(myfile, "%d %s", x, s);
printf("I have %d %s.\n", x, s);
/* set pointer to beginning of file */
rewind(myfile);
fscanf(myfile, "%d %s", &x, &s);
printf("I ate %d %s.\n", x, s);
fclose(myfile);
}
}
Output:
I have 10 cookies.
I ate 10 cookies.
DS50001456J-page 84
 2004-2014 Microchip Technology Inc.
Standard C Libraries
scanf
Description:
Scans formatted text from stdin.
Include:
<stdio.h>
Prototype:
int scanf(const char *format, ...);
Argument:
format
format control string
...
optional arguments
Return Value:
Returns the number of items successfully converted and assigned. If
no items are assigned, a 0 is returned. EOF is returned if an input
failure is encountered before the first.
Remarks:
Each format specifier begins with a percent sign followed by optional
fields and a required type as shown here:
%[*][width][modifier]type
*
indicates assignment suppression. This will cause the input field to be
skipped and no assignment made.
width
specify the maximum number of input characters to match for the conversion, not including white space that can be skipped.
modifier
h modifier –
h modifier –
l modifier –
l modifier –
l modifier –
l modifier –
ll modifier –
ll modifier –
L modifier –
 2004-2014 Microchip Technology Inc.
used with type d, i, o, u, x, X; converts the value to a
short int or unsigned short int.
used with n; specifies that the pointer points to a short
int
used with type d, i, o, u, x, X; converts the value to a
long int or unsigned long int
used with n; specifies that the pointer points to a long
int
used with c; specifies a wide character
used with type e, E, f, F, g, G; converts the value to a
double
used with type d, i, o, u, x, X; converts the value to a
long long int or unsigned long long int
used with n; specifies that the pointer points to a long
long int
used with e, E, f, g, G; converts the value to a long
double
DS50001456J-page 85
16-Bit Language Tools Libraries
scanf (Continued)
type
d,i
o
u
x
X
e,E
f
g,G
c
s
p
n
[...]
%
Example:
signed int
unsigned int in octal
unsigned int in decimal
unsigned int in lowercase hexadecimal
unsigned int in uppercase hexadecimal
double in scientific notation
double decimal notation
double (takes the form of e, E or f as appropriate)
char - a single character
string
value of a pointer
the associated argument shall be an integer pointer into,
which is placed the number of characters read so far.
No characters are scanned.
character array. Allows a search of a set of characters.
A caret (^) immediately after the left bracket ( [ ) inverts
the scanset and allows any ASCII character except
those specified between the brackets. A dash character
(-) may be used to specify a range beginning with the
character before the dash and ending the character
after the dash. A null character can not be part of the
scanset.
A % character is scanned
For MPLAB SIM simulator.
#include <stdio.h> /* for scanf, printf */
#include <libpic30.h>
int main(void)
{
int number, items;
char letter;
char color[30], string[30];
float salary;
__attach_input_file("UartIn.txt");
printf("Enter your favorite number, "
"favorite letter, ");
printf("favorite color desired salary "
"and SSN:\n");
items = scanf("%d %c %[A-Za-z] %f %s", &number,
&letter, &color, &salary, &string);
printf("Number of items scanned = %d\n", items);
printf("Favorite number = %d, ", number);
printf("Favorite letter = %c\n", letter);
printf("Favorite color = %s, ", color);
printf("Desired salary = $%.2f\n", salary);
printf("Social Security Number = %s, ", string);
}
If not using the simulator, remove these lines:
#include <libpic30.h>
__attach_input_file("uart_in.txt");
Input:
Contents of UartIn.txt (used as stdin input for simulator):
5 T Green 300000 123-45-6789
DS50001456J-page 86
 2004-2014 Microchip Technology Inc.
Standard C Libraries
scanf (Continued)
Output:
Enter your favorite number, favorite letter,
favorite color, desired salary and SSN:
Number of items scanned = 5
Favorite number = 5, Favorite letter = T
Favorite color = Green, Desired salary = $300000.00
Social Security Number = 123-45-6789
setbuf
Description:
Defines how a stream is buffered.
Include:
<stdio.h>
Prototype:
void setbuf(FILE *stream, char *buf);
Arguments:
stream
pointer to the open stream
buf
user allocated buffer
Remarks:
setbuf must be called after fopen but before any other function calls
that operate on the stream. If buf is a null pointer, setbuf calls the
function setvbuf(stream, 0, _IONBF, BUFSIZ) for no buffering;
otherwise setbuf calls setvbuf(stream, buf, _IOFBF,
BUFSIZ) for full buffering with a buffer of size BUFSIZ. See setvbuf.
This function requires a heap.
Example:
#include <stdio.h> /* for setbuf, printf, */
/* fopen, fclose,
*/
/* FILE, NULL, BUFSIZ */
int main(void)
{
FILE *myfile1, *myfile2;
char buf[BUFSIZ];
if ((myfile1 = fopen("afile1", "w+")) != NULL)
{
setbuf(myfile1, NULL);
printf("myfile1 has no buffering\n");
fclose(myfile1);
}
if ((myfile2 = fopen("afile2", "w+")) != NULL)
{
setbuf(myfile2, buf);
printf("myfile2 has full buffering");
fclose(myfile2);
}
}
Output:
myfile1 has no buffering
myfile2 has full buffering
 2004-2014 Microchip Technology Inc.
DS50001456J-page 87
16-Bit Language Tools Libraries
setvbuf
Description:
Defines the stream to be buffered and the buffer size.
Include:
<stdio.h>
Prototype:
int setvbuf(FILE *stream, char *buf, int mode,
size_t size);
Arguments:
stream
pointer to the open stream
buf
user allocated buffer
mode
type of buffering
size
size of buffer
Return Value:
Returns 0 if successful
Remarks:
setvbuf must be called after fopen but before any other function
calls that operate on the stream. For mode, use one of the following:
_IOFBF – for full buffering
_IOLBF – for line buffering
_IONBF – for no buffering
This function requires a heap.
Example:
#include <stdio.h> /* for setvbuf, fopen, */
/* printf, FILE, NULL, */
/* _IONBF, _IOFBF
*/
int main(void)
{
FILE *myfile1, *myfile2;
char buf[256];
if ((myfile1 = fopen("afile1", "w+")) != NULL)
{
if (setvbuf(myfile1, NULL, _IONBF, 0) == 0)
printf("myfile1 has no buffering\n");
else
printf("Unable to define buffer stream "
"and/or size\n");
}
fclose(myfile1);
if ((myfile2 = fopen("afile2", "w+")) != NULL)
{
if (setvbuf(myfile2, buf, _IOFBF, sizeof(buf)) ==
0)
printf("myfile2 has a buffer of %d "
"characters\n", sizeof(buf));
else
printf("Unable to define buffer stream "
"and/or size\n");
}
fclose(myfile2);
}
Output:
myfile1 has no buffering
myfile2 has a buffer of 256 characters
DS50001456J-page 88
 2004-2014 Microchip Technology Inc.
Standard C Libraries
sprintf
Description:
Prints formatted text to a string.
Include:
<stdio.h>
Prototype:
int sprintf(char *s, const char *format, ...);
Arguments:
s
storage string for output
format
format control string
...
optional arguments
Return Value:
Returns the number of characters stored in s excluding the terminating
null character.
Remarks:
The format argument has the same syntax and use that it has in
printf.
Example:
#include <stdio.h> /* for sprintf, printf */
int main(void)
{
char sbuf[100], s[]="Print this string";
int x = 1, y;
char a = '\n';
y = sprintf(sbuf, "%s %d time%c", s, x, a);
printf("Number of characters printed to "
"string buffer = %d\n", y);
printf("String = %s\n", sbuf);
}
Output:
Number of characters printed to string buffer = 25
String = Print this string 1 time
sscanf
Description:
Scans formatted text from a string.
Include:
<stdio.h>
Prototype:
int sscanf(const char *s, const char *format, ...);
Arguments:
s
storage string for input
format
format control string
...
optional arguments
Return Value:
Returns the number of items successfully converted and assigned. If
no items are assigned, a 0 is returned. EOF is returned if an input error
is encountered before the first conversion.
Remarks:
The format argument has the same syntax and use that it has in
scanf.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 89
16-Bit Language Tools Libraries
sscanf (Continued)
Example:
#include <stdio.h> /* for sscanf, printf */
int main(void)
{
char s[] = "5 T green 3000000.00";
int number, items;
char letter;
char color[10];
float salary;
items = sscanf(s, "%d %c %s %f", &number, &letter,
&color, &salary);
printf("Number of items scanned = %d\n", items);
printf("Favorite number = %d\n", number);
printf("Favorite letter = %c\n", letter);
printf("Favorite color = %s\n", color);
printf("Desired salary = $%.2f\n", salary);
}
Output:
Number of items scanned = 4
Favorite number = 5
Favorite letter = T
Favorite color = green
Desired salary = $3000000.00
tmpfileprintf
Description:
Creates a temporary file.
Include:
<stdio.h>
Prototype:
FILE *tmpfile(void)
Return Value:
Returns a stream pointer if successful; otherwise, returns a NULL
pointer.
Remarks:
tmpfile creates a file with a unique filename. The temporary file is
opened in w+b (binary read/write) mode. It will automatically be
removed when exit is called; otherwise the file will remain in the
directory. This function requires a heap.
Example:
#include <stdio.h> /* for tmpfile, printf, */
/* FILE, NULL
*/
int main(void)
{
FILE *mytempfile;
if ((mytempfile = tmpfile()) == NULL)
printf("Cannot create temporary file");
else
printf("Temporary file was created");
}
Output:
Temporary file was created
DS50001456J-page 90
 2004-2014 Microchip Technology Inc.
Standard C Libraries
tmpnam
Description:
Creates a unique temporary filename.
Include:
<stdio.h>
Prototype:
char *tmpnam(char *s);
Argument:
s
Return Value:
Returns a pointer to the filename generated and stores the filename in
s. If it can not generate a filename, the NULL pointer is returned.
Remarks:
The created filename will not conflict with an existing file name. Use
L_tmpnam to define the size of array the argument of tmpnam points
to.
Example:
#include <stdio.h> /* for tmpnam, L_tmpnam, */
/* printf, NULL
*/
pointer to the temporary name
int main(void)
{
char *myfilename;
char mybuf[L_tmpnam];
char *myptr = (char *) &mybuf;
if ((myfilename = tmpnam(myptr)) == NULL)
printf("Cannot create temporary file name");
else
printf("Temporary file %s was created",
myfilename);
}
Output:
Temporary file ctm00001.tmp was created
ungetc
Description:
Pushes character back onto stream.
Include:
<stdio.h>
Prototype:
int ungetc(int c, FILE *stream);
Argument:
c
character to be pushed back
stream
pointer to the open stream
Return Value:
Returns the pushed character if successful; otherwise, returns EOF.
Remarks:
The pushed back character will be returned by a subsequent read on
the stream. If more than one character is pushed back, they will be
returned in the reverse order of their pushing. A successful call to a file
positioning function (fseek, fsetpos or rewind) cancels any pushed
back characters. Only one character of push back is guaranteed.
Multiple calls to ungetc without an intervening read or file positioning
operation may cause a failure.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 91
16-Bit Language Tools Libraries
ungetc (Continued)
Example:
#include <stdio.h> /* for ungetc, fgetc,
*/
/* printf, fopen, fclose, */
/* FILE, NULL, EOF
*/
int main(void)
{
FILE *buf;
char y, c;
if ((buf = fopen("afile.txt", "r")) == NULL)
printf("Cannot open afile.txt\n");
else
{
y = fgetc(buf);
while (y != EOF)
{
if (y == 'r')
{
c = ungetc(y, buf);
if (c != EOF)
{
printf("2");
y = fgetc(buf);
}
}
printf("%c", y);
y = fgetc(buf);
}
fclose(buf);
}
}
Input:
Contents of afile.txt (used as input):
Short
Longer string
Output:
Sho2rt
Longe2r st2ring
DS50001456J-page 92
 2004-2014 Microchip Technology Inc.
Standard C Libraries
vasprintf
Description:
Prints formatted text to a string using a variable length argument list.
Include:
<stdio.h>
<stdarg.h>
Prototype:
int vasprintf(char **s, const char *format,
va_list ap);
Arguments:
s
storage string for output
format
format control string
ap
pointer to a list of arguments
Return Value:
Returns number of characters stored in s excluding the terminating null
character.
Remarks:
The format argument has the same syntax and use that it has in
printf.
To access the variable length argument list, the ap variable must be initialized by the macro va_start and may be reinitialized by additional
calls to va_arg. This must be done before the vasprintf function is
called. Invoke va_end after the function returns. For more details, see
stdarg.h
This function requires a heap.
Example:
#include <stdio.h>
#include <stdarg.h>
/* for vasprintf, printf */
/* for va_start,
*/
/* va_list, va_end
*/
void errmsg(const char *fmt, ...)
{
va_list ap;
char buf[100];
char **bufptr;
bufptr = &buf;
va_start(ap, fmt);
vasprintf(bufptr, fmt, ap);
va_end(ap);
printf("Error: %s", buf);
}
int main(void)
{
int num = 3;
errmsg("The letter '%c' is not %s\n", 'a',
"an integer value.");
errmsg("Requires %d%s\n", num,
" or more characters.\n");
}
Output:
Error: The letter 'a' is not an integer value.
Error: Requires 3 or more characters.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 93
16-Bit Language Tools Libraries
vfprintf
Description:
Prints formatted data to a stream using a variable length argument list.
Include:
<stdio.h>
<stdarg.h>
Prototype:
int vfprintf(FILE *stream, const char *format,
va_list ap);
Arguments:
stream
pointer to the open stream
format
format control string
ap
pointer to a list of arguments
Return Value:
Returns number of characters generated or a negative number if an
error occurs.
Remarks:
The format argument has the same syntax and use that it has in
printf.
To access the variable length argument list, the ap variable must be initialized by the macro va_start and may be reinitialized by additional
calls to va_arg. This must be done before the vfprintf function is
called. Invoke va_end after the function returns. For more details, see
stdarg.h.
This function requires a heap.
Example:
#include <stdio.h>
/* for vfprintf, fopen, */
/* fclose, printf,
*/
/* FILE, NULL
*/
#include <stdarg.h> /* for va_start,
/* va_list, va_end
*/
*/
FILE *myfile;
void errmsg(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
vfprintf(myfile, fmt, ap);
va_end(ap);
}
int main(void)
{
int num = 3;
if ((myfile = fopen("afile.txt", "w")) == NULL)
printf("Cannot open afile.txt\n");
else
{
errmsg("Error: The letter '%c' is not %s\n", 'a',
"an integer value.");
errmsg("Error: Requires %d%s%c", num,
" or more characters.", '\n');
}
fclose(myfile);
}
Output:
Contents of afile.txt
Error: The letter 'a' is not an integer value.
Error: Requires 3 or more characters.
DS50001456J-page 94
 2004-2014 Microchip Technology Inc.
Standard C Libraries
vprintf
Description:
Prints formatted text to stdout using a variable length argument list.
Include:
<stdio.h>
<stdarg.h>
Prototype:
int vprintf(const char *format, va_list ap);
Arguments:
format
format control string
ap
pointer to a list of arguments
Return Value:
Returns number of characters generated or a negative number if an
error occurs.
Remarks:
The format argument has the same syntax and use that it has in
printf.
To access the variable length argument list, the ap variable must be initialized by the macro va_start and may be reinitialized by additional
calls to va_arg. This must be done before the vprintf function is
called. Invoke va_end after the function returns. For more details, see
stdarg.h
Example:
#include <stdio.h>
#include <stdarg.h>
/* for vprintf, printf */
/* for va_start,
*/
/* va_list, va_end
*/
void errmsg(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
printf("Error: ");
vprintf(fmt, ap);
va_end(ap);
}
int main(void)
{
int num = 3;
errmsg("The letter '%c' is not %s\n", 'a',
"an integer value.");
errmsg("Requires %d%s\n", num,
" or more characters.\n");
}
Output:
Error: The letter 'a' is not an integer value.
Error: Requires 3 or more characters.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 95
16-Bit Language Tools Libraries
vsprintf
Description:
Prints formatted text to a string using a variable length argument list.
Include:
<stdio.h>
<stdarg.h>
Prototype:
int vsprintf(char *s, const char *format, va_list
ap);
Arguments:
s
storage string for output
format
format control string
ap
pointer to a list of arguments
Return Value:
Returns number of characters stored in s excluding the terminating null
character.
Remarks:
The format argument has the same syntax and use that it has in
printf.
To access the variable length argument list, the ap variable must be initialized by the macro va_start and may be reinitialized by additional
calls to va_arg. This must be done before the vsprintf function is
called. Invoke va_end after the function returns. For more details, see
stdarg.h
This function requires a heap.
Example:
#include <stdio.h>
#include <stdarg.h>
/* for vsprintf, printf */
/* for va_start,
*/
/* va_list, va_end
*/
void errmsg(const char *fmt, ...)
{
va_list ap;
char buf[100];
va_start(ap, fmt);
vsprintf(buf, fmt, ap);
va_end(ap);
printf("Error: %s", buf);
}
int main(void)
{
int num = 3;
errmsg("The letter '%c' is not %s\n", 'a',
"an integer value.");
errmsg("Requires %d%s\n", num,
" or more characters.\n");
}
Output:
Error: The letter 'a' is not an integer value.
Error: Requires 3 or more characters.
DS50001456J-page 96
 2004-2014 Microchip Technology Inc.
Standard C Libraries
2.14
<STDLIB.H> UTILITY FUNCTIONS
The header file stdlib.h consists of types, macros and functions that provide text
conversions, memory management, searching and sorting abilities and other general
utilities.
div_t
Description:
A type that holds a quotient and remainder of a signed integer division
with operands of type int.
Include:
<stdlib.h>
Prototype:
typedef struct { int quot, rem; } div_t;
Remarks:
This is the structure type returned by the function, div.
ldiv_t
Description:
A type that holds a quotient and remainder of a signed integer division
with operands of type long.
Include:
<stdlib.h>
Prototype:
typedef struct { long quot, rem; } ldiv_t;
Remarks:
This is the structure type returned by the function, ldiv.
size_t
Description:
The type of the result of the sizeof operator.
Include:
<stdlib.h>
wchar_t
Description:
A type that holds a wide character value.
Include:
<stdlib.h>
EXIT_FAILURE
Description:
Reports unsuccessful termination.
Include:
<stdlib.h>
Remarks:
EXIT_FAILURE is a value for the exit function to return an unsuccessful
termination status.
Example:
See exit for example of use.
EXIT_SUCCESS
Description:
Reports successful termination.
Include:
<stdlib.h>
Remarks:
EXIT_SUCCESS is a value for the exit function to return a successful
termination status.
Example:
See exit for example of use.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 97
16-Bit Language Tools Libraries
MB_CUR_MAX
Description:
Maximum number of characters in a multibyte character.
Include:
<stdlib.h>
Value:
1
NULL
Description:
The value of a null pointer constant.
Include:
<stdlib.h>
RAND_MAX
Description:
Maximum value capable of being returned by the rand function.
Include:
<stdlib.h>
Value:
32767
abort
Description:
Aborts the current process.
Include:
<stdlib.h>
Prototype:
void abort(void);
Remarks:
abort will cause the processor to reset.
Example:
#include <stdio.h>
/* for fopen, fclose, */
/* printf, FILE, NULL */
#include <stdlib.h> /* for abort
*/
int main(void)
{
FILE *myfile;
if ((myfile = fopen("samp.fil", "r")) == NULL)
{
printf("Cannot open samp.fil\n");
abort();
}
else
printf("Success opening samp.fil\n");
fclose(myfile);
}
Output:
Cannot open samp.fil
ABRT
DS50001456J-page 98
 2004-2014 Microchip Technology Inc.
Standard C Libraries
abs
Description:
Calculates the absolute value.
Include:
<stdlib.h>
Prototype:
int abs(int i);
Argument:
i
Return Value:
Returns the absolute value of i.
Remarks:
A negative number is returned as positive; a positive number is
unchanged.
Example:
#include <stdio.h> /* for printf */
#include <stdlib.h> /* for abs
*/
integer value
int main(void)
{
int i;
i = 12;
printf("The absolute value of
i, abs(i));
%d is
i = -2;
printf("The absolute value of
i, abs(i));
%d is
i = 0;
printf("The absolute value of
i, abs(i));
%d is
%d\n",
%d\n",
%d\n",
}
Output:
The absolute value of
The absolute value of
The absolute value of
12 is
-2 is
0 is
12
2
0
atexit
Description:
Registers the specified function to be called when the program
terminates normally.
Include:
<stdlib.h>
Prototype:
int atexit(void(*func)(void));
Argument:
func
Return Value:
Returns a zero if successful; otherwise, returns a non-zero value.
Remarks:
For the registered functions to be called, the program must terminate
with the exit function call.
Example:
#include <stdio.h> /* for scanf, printf */
#include <stdlib.h> /* for atexit, exit */
function to be called
void good_msg(void);
void bad_msg(void);
void end_msg(void);
 2004-2014 Microchip Technology Inc.
DS50001456J-page 99
16-Bit Language Tools Libraries
atexit (Continued)
int main(void)
{
int number;
atexit(end_msg);
printf("Enter your favorite number:");
scanf("%d", &number);
printf(" %d\n", number);
if (number == 5)
{
printf("Good Choice\n");
atexit(good_msg);
exit(0);
}
else
{
printf("%d!?\n", number);
atexit(bad_msg);
exit(0);
}
}
void good_msg(void)
{
printf("That's an excellent number\n");
}
void bad_msg(void)
{
printf("That's an awful number\n");
}
void end_msg(void)
{
printf("Now go count something\n");
}
Input:
With contents of UartIn.txt (used as stdin input for simulator):
5
Output:
Enter your favorite number: 5
Good Choice
That's an excellent number
Now go count something
Input:
With contents of UartIn.txt (used as stdin input for simulator):
42
Output:
Enter your favorite number: 42
42!?
That's an awful number
Now go count something
DS50001456J-page 100
 2004-2014 Microchip Technology Inc.
Standard C Libraries
atof
Description:
Converts a string to a double precision floating-point value.
Include:
<stdlib.h>
Prototype:
double atof(const char *s);
Argument:
s
Return Value:
Returns the converted value if successful; otherwise, returns 0.
Remarks:
The number may consist of the following:
[whitespace] [sign] digits [.digits]
[ { e | E }[sign]digits]
optional whitespace followed by an optional sign, then a sequence
of one or more digits with an optional decimal point, followed by one
or more optional digits and an optional e or E followed by an optional
signed exponent. The conversion stops when the first unrecognized
character is reached. The conversion is the same as strtod(s,0)
except it does no error checking so errno will not be set.
Example:
#include <stdio.h> /* for printf */
#include <stdlib.h> /* for atof
*/
pointer to the string to be converted
int main(void)
{
char a[] = " 1.28";
char b[] = "27.835e2";
char c[] = "Number1";
double x;
x = atof(a);
printf("String = \"%s\" float = %f\n", a, x);
x = atof(b);
printf("String = \"%s\" float = %f\n", b, x);
x = atof(c);
printf("String = \"%s\"
float = %f\n", c, x);
}
Output:
String = "1.28"
float = 1.280000
String = "27.835:e2" float = 2783.500000
String = "Number1" float = 0.000000
 2004-2014 Microchip Technology Inc.
DS50001456J-page 101
16-Bit Language Tools Libraries
atoi
Description:
Converts a string to an integer.
Include:
<stdlib.h>
Prototype:
int atoi(const char *s);
Argument:
s
Return Value:
Returns the converted integer if successful; otherwise, returns 0.
Remarks:
The number may consist of the following:
[whitespace] [sign] digits
optional whitespace followed by an optional sign, then a sequence
of one or more digits. The conversion stops when the first unrecognized character is reached. The conversion is equivalent to (int)
strtol(s,0,10), except it does no error checking so errno will not
be set.
Example:
#include <stdio.h> /* for printf */
#include <stdlib.h> /* for atoi
*/
string to be converted
int main(void)
{
char a[] = " -127";
char b[] = "Number1";
int x;
x = atoi(a);
printf("String = \"%s\"\tint = %d\n", a, x);
x = atoi(b);
printf("String = \"%s\"\tint = %d\n", b, x);
}
Output:
String = " -127"
String = "Number1"
int = -127
int = 0
atol
DS50001456J-page 102
Description:
Converts a string to a long integer.
Include:
<stdlib.h>
Prototype:
long atol(const char *s);
Argument:
s
Return Value:
Returns the converted long integer if successful; otherwise, returns 0.
Remarks:
The number may consist of the following:
[whitespace] [sign] digits
optional whitespace followed by an optional sign, then a sequence
of one or more digits. The conversion stops when the first unrecognized character is reached. The conversion is equivalent to (int)
strtol(s,0,10), except it does no error checking so errno will not
be set.
string to be converted
 2004-2014 Microchip Technology Inc.
Standard C Libraries
atol (Continued)
Example:
#include <stdio.h> /* for printf */
#include <stdlib.h> /* for atol
*/
int main(void)
{
char a[] = " -123456";
char b[] = "2Number";
long x;
x = atol(a);
printf("String = \"%s\"
int = %ld\n", a, x);
x = atol(b);
printf("String = \"%s\"
int = %ld\n", b, x);
}
Output:
String = " -123456"
String = "2Number"
int = -123456
int = 2
bsearch
Description:
Performs a binary search.
Include:
<stdlib.h>
Prototype:
void *bsearch(const void *key, const void *base,
size_t nelem, size_t size,
int (*cmp)(const void *ck, const void *ce));
Arguments:
key
object to search for
base
pointer to the start of the search data
nelem
number of elements
size
size of elements
cmp
pointer to the comparison function
ck
pointer to the key for the search
ce
pointer to the element being compared with the key.
Return Value:
Returns a pointer to the object being searched for if found; otherwise,
returns NULL.
Remarks:
The value returned by the compare function is <0 if ck is less than ce,
0 if ck is equal to ce or >0 if ck is greater than ce.
In the following example, qsort is used to sort the list before bsearch
is called. bsearch requires the list to be sorted according to the
comparison function. This comp uses ascending order.
 2004-2014 Microchip Technology Inc.
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16-Bit Language Tools Libraries
bsearch (Continued)
Example:
#include <stdlib.h> /* for bsearch, qsort */
#include <stdio.h> /* for printf, sizeof */
#define NUM 7
int comp(const void *e1, const void *e2);
int main(void)
{
int list[NUM] = {35, 47, 63, 25, 93, 16, 52};
int x, y;
int *r;
qsort(list, NUM, sizeof(int), comp);
printf("Sorted List:
");
for (x = 0; x < NUM; x++)
printf("%d ", list[x]);
y = 25;
r = bsearch(&y, list, NUM, sizeof(int), comp);
if (r)
printf("\nThe value %d was found\n", y);
else
printf("\nThe value %d was not found\n", y);
y = 75;
r = bsearch(&y, list, NUM, sizeof(int), comp);
if (r)
printf("\nThe value %d was found\n", y);
else
printf("\nThe value %d was not found\n", y);
}
int comp(const void *e1, const void *e2)
{
const int * a1 = e1;
const int * a2 = e2;
if (*a1 < *a2)
return -1;
else if (*a1 == *a2)
return 0;
else
return 1;
}
Output:
Sorted List:
16 25 35
The value 25 was found
47
52
63
93
The value 75 was not found
DS50001456J-page 104
 2004-2014 Microchip Technology Inc.
Standard C Libraries
calloc
Description:
Allocates an array in memory and initializes the elements to 0.
Include:
<stdlib.h>
Prototype:
void *calloc(size_t nelem, size_t size);
Arguments:
nelem
number of elements
size
length of each element
Return Value:
Returns a pointer to the allocated space if successful; otherwise,
returns a null pointer.
Remarks:
Memory returned by calloc is aligned correctly for any size data
element and is initialized to zero. This function requires a heap.
Example:
/* This program allocates memory for the
*/
/* array 'i' of long integers and initializes */
/* them to zero.
*/
#include <stdio.h> /* for printf, NULL */
#include <stdlib.h> /* for calloc, free */
int main(void)
{
int x;
long *i;
i = (long *)calloc(5, sizeof(long));
if (i != NULL)
{
for (x = 0; x < 5; x++)
printf("i[%d] = %ld\n", x, i[x]);
free(i);
}
else
printf("Cannot allocate memory\n");
}
Output:
i[0] =
i[1] =
i[2] =
i[3] =
i[4] =
0
0
0
0
0
div
Description:
Calculates the quotient and remainder of two numbers.
Include:
<stdlib.h>
Prototype:
div_t div(int numer, int denom);
Arguments:
numer
numerator
denom
denominator
Return Value:
Returns the quotient and the remainder.
Remarks:
The returned quotient will have the same sign as the numerator divided
by the denominator. The sign for the remainder will be such that the
quotient times the denominator plus the remainder will equal the
numerator (quot * denom + rem = numer). Division by zero will invoke
the math exception error, which, by default, will cause a Reset. Write a
math error handler to do something else.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 105
16-Bit Language Tools Libraries
div (Continued)
Example:
#include <stdlib.h> /* for div, div_t */
#include <stdio.h> /* for printf
*/
void __attribute__((__interrupt__))
_MathError(void)
{
printf("Illegal instruction executed\n");
abort();
}
int main(void)
{
int x, y;
div_t z;
x = 7;
y = 3;
printf("For div(%d, %d)\n", x, y);
z = div(x, y);
printf("The quotient is %d and the "
"remainder is %d\n\n", z.quot, z.rem);
x = 7;
y = -3;
printf("For div(%d, %d)\n", x, y);
z = div(x, y);
printf("The quotient is %d and the "
"remainder is %d\n\n", z.quot, z.rem);
x = -5;
y = 3;
printf("For div(%d, %d)\n", x, y);
z = div(x, y);
printf("The quotient is %d and the "
"remainder is %d\n\n", z.quot, z.rem);
x = 7;
y = 7;
printf("For div(%d, %d)\n", x, y);
z = div(x, y);
printf("The quotient is %d and the "
"remainder is %d\n\n", z.quot, z.rem);
x = 7;
y = 0;
printf("For div(%d, %d)\n", x, y);
z = div(x, y);
printf("The quotient is %d and the "
"remainder is %d\n\n", z.quot, z.rem);
}
DS50001456J-page 106
 2004-2014 Microchip Technology Inc.
Standard C Libraries
div (Continued)
Output:
For div(7, 3)
The quotient is 2 and the remainder is 1
For div(7, -3)
The quotient is -2 and the remainder is 1
For div(-5, 3)
The quotient is -1 and the remainder is -2
For div(7, 7)
The quotient is 1 and the remainder is 0
For div(7, 0)
Illegal instruction executed
ABRT
exit
Description:
Terminates program after clean up.
Include:
<stdlib.h>
Prototype:
void exit(int status);
Argument:
status
Remarks:
exit calls any functions registered by atexit in reverse order of registration, flushes buffers, closes stream, closes any temporary files
created with tmpfile and resets the processor. This function is
customizable. See pic30-libs.
Example:
#include <stdio.h>
exit status
/* for fopen, printf, */
/* FILE, NULL
*/
#include <stdlib.h> /* for exit
*/
int main(void)
{
FILE *myfile;
if ((myfile = fopen("samp.fil", "r" )) == NULL)
{
printf("Cannot open samp.fil\n");
exit(EXIT_FAILURE);
}
else
{
printf("Success opening samp.fil\n");
exit(EXIT_SUCCESS);
}
printf("This will not be printed");
}
Output:
Cannot open samp.fil
 2004-2014 Microchip Technology Inc.
DS50001456J-page 107
16-Bit Language Tools Libraries
free
Description:
Frees memory.
Include:
<stdlib.h>
Prototype:
void free(void *ptr);
Argument:
ptr
Remarks:
Frees memory previously allocated with calloc, malloc or realloc.
If free is used on space that has already been deallocated (by a previous call to free or by realloc) or on space not allocated with calloc, malloc or realloc, the behavior is undefined. This function
requires a heap.
Example:
#include <stdio.h>
points to memory to be freed
/* for printf, sizeof, */
/* NULL
*/
#include <stdlib.h> /* for malloc, free
*/
int main(void)
{
long *i;
if ((i = (long *)malloc(50 * sizeof(long))) ==
NULL)
printf("Cannot allocate memory\n");
else
{
printf("Memory allocated\n");
free(i);
printf("Memory freed\n");
}
}
Output:
Memory allocated
Memory freed
getenv
DS50001456J-page 108
Description:
Get a value for an environment variable.
Include:
<stdlib.h>
Prototype:
char *getenv(const char *name);
Argument:
name
Return Value:
Returns a pointer to the value of the environment variable if successful;
otherwise, returns a null pointer.
Remarks:
This function must be customized to be used as described (see
pic30-libs). By default, there are no entries in the environment list
for getenv to find.
name of environment variable
 2004-2014 Microchip Technology Inc.
Standard C Libraries
getenv (Continued)
Example:
#include <stdio.h> /* for printf, NULL */
#include <stdlib.h> /* for getenv
*/
int main(void)
{
char *incvar;
incvar = getenv("INCLUDE");
if (incvar != NULL)
printf("INCLUDE environment variable = %s\n",
incvar);
else
printf("Cannot find environment variable "
"INCLUDE ");
}
Output:
Cannot find environment variable INCLUDE
labs
Description:
Calculates the absolute value of a long integer.
Include:
<stdlib.h>
Prototype:
long labs(long i);
Argument:
i
Return Value:
Returns the absolute value of i.
Remarks:
A negative number is returned as positive; a positive number is
unchanged.
Example:
#include <stdio.h> /* for printf */
#include <stdlib.h> /* for labs
*/
long integer value
int main(void)
{
long i;
i = 123456;
printf("The absolute value of %7ld is %6ld\n",
i, labs(i));
i = -246834;
printf("The absolute value of %7ld is %6ld\n",
i, labs(i));
i = 0;
printf("The absolute value of %7ld is %6ld\n",
i, labs(i));
}
Output:
The absolute value of 123456 is 123456
The absolute value of -246834 is 246834
The absolute value of
0 is
0
 2004-2014 Microchip Technology Inc.
DS50001456J-page 109
16-Bit Language Tools Libraries
ldiv
Description:
Calculates the quotient and remainder of two long integers.
Include:
<stdlib.h>
Prototype:
ldiv_t ldiv(long numer, long denom);
Arguments:
numer
numerator
denom
denominator
Return Value:
Returns the quotient and the remainder.
Remarks:
The returned quotient will have the same sign as the numerator divided
by the denominator. The sign for the remainder will be such that the
quotient times the denominator plus the remainder will equal the
numerator (quot * denom + rem = numer). If the denominator is zero,
the behavior is undefined.
Example:
#include <stdlib.h> /* for ldiv, ldiv_t */
#include <stdio.h> /* for printf
*/
int main(void)
{
long x,y;
ldiv_t z;
x = 7;
y = 3;
printf("For ldiv(%ld, %ld)\n", x, y);
z = ldiv(x, y);
printf("The quotient is %ld and the "
"remainder is %ld\n\n", z.quot, z.rem);
x = 7;
y = -3;
printf("For ldiv(%ld, %ld)\n", x, y);
z = ldiv(x, y);
printf("The quotient is %ld and the "
"remainder is %ld\n\n", z.quot, z.rem);
x = -5;
y = 3;
printf("For ldiv(%ld, %ld)\n", x, y);
z = ldiv(x, y);
printf("The quotient is %ld and the "
"remainder is %ld\n\n", z.quot, z.rem);
x = 7;
y = 7;
printf("For ldiv(%ld, %ld)\n", x, y);
z = ldiv(x, y);
printf("The quotient is %ld and the "
"remainder is %ld\n\n", z.quot, z.rem);
x = 7;
y = 0;
printf("For ldiv(%ld, %ld)\n", x, y);
z = ldiv(x, y);
printf("The quotient is %ld and the "
"remainder is %ld\n\n",
z.quot, z.rem);
}
DS50001456J-page 110
 2004-2014 Microchip Technology Inc.
Standard C Libraries
ldiv (Continued)
Output:
For ldiv(7, 3)
The quotient is 2 and the remainder is 1
For ldiv(7, -3)
The quotient is -2 and the remainder is 1
For ldiv(-5, 3)
The quotient is -1 and the remainder is -2
For ldiv(7, 7)
The quotient is 1 and the remainder is 0
For ldiv(7, 0)
The quotient is -1 and the remainder is 7
Explanation:
In the last example (ldiv(7,0)) the denominator is zero, the behavior
is undefined.
malloc
Description:
Allocates memory.
The default implementation of malloc will require an additional 4 bytes
of heap memory per allocation.
The legacy library's malloc will use an additional 2 bytes of heap
memory per allocation.
Include:
<stdlib.h>
Prototype:
void *malloc(size_t size);
Argument:
size
Return Value:
Returns a pointer to the allocated space if successful; otherwise,
returns a null pointer.
Remarks:
malloc does not initialize memory it returns.
This function requires a heap.
Example:
#include <stdio.h>
number of characters to allocate
/* for printf, sizeof, */
/* NULL
*/
#include <stdlib.h> /* for malloc, free
*/
int main(void)
{
long *i;
if ((i = (long *)malloc(50 * sizeof(long))) ==
NULL)
printf("Cannot allocate memory\n");
else
{
printf("Memory allocated\n");
free(i);
printf("Memory freed\n");
}
}
Output:
Memory allocated
Memory freed
 2004-2014 Microchip Technology Inc.
DS50001456J-page 111
16-Bit Language Tools Libraries
DS50001456J-page 112
 2004-2014 Microchip Technology Inc.
Standard C Libraries
mblen
Description:
Gets the length of a multibyte character. (See Remarks.)
Include:
<stdlib.h>
Prototype:
int mblen(const char *s, size_t n);
Arguments:
s
points to the multibyte character
n
number of bytes to check
Return Value:
Returns zero if s points to a null character; otherwise, returns 1.
Remarks:
The 16-bit compiler does not support multibyte characters with length
greater than 1 byte.
mbstowcs
Description:
Converts a multibyte string to a wide character string. (See Remarks.)
Include:
<stdlib.h>
Prototype:
size_t mbstowcs(wchar_t *wcs, const char *s,
size_t n);
Arguments:
wcs
points to the wide character string
s
points to the multibyte string
n
the number of wide characters to convert.
Return Value:
Returns the number of wide characters stored excluding the null
character.
Remarks:
mbstowcs converts n number of wide characters unless it encounters
a null wide character first. The 16-bit compiler does not support
multibyte characters with length greater than 1 byte.
mbtowc
Description:
Converts a multibyte character to a wide character. (See Remarks).
Include:
<stdlib.h>
Prototype:
int mbtowc(wchar_t *pwc, const char *s, size_t n);
Arguments:
pwc
points to the wide character
s
points to the multibyte character
n
number of bytes to check
Return Value:
Returns zero if s points to a null character; otherwise, returns 1.
Remarks:
The resulting wide character will be stored at pwc. The 16-bit compiler
does not support multibyte characters with length greater than 1 byte.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 113
16-Bit Language Tools Libraries
qsort
Description:
Performs a quick sort.
Include:
<stdlib.h>
Prototype:
void qsort(void *base, size_t nelem, size_t size,
int (*cmp)(const void *e1, const void *e2));
Arguments:
base
pointer to the start of the array
nelem
number of elements
size
size of the elements
cmp
pointer to the comparison function
e1
pointer to the key for the search
e2
pointer to the element being compared with the key
Remarks:
qsort overwrites the array with the sorted array. The comparison function is supplied by the user. In the following example, the list is sorted
according to the comparison function. This comp uses ascending order.
This function requires a heap.
Example:
#include <stdlib.h> /* for qsort */
#include <stdio.h> /* for printf */
#define NUM 7
int comp(const void *e1, const void *e2);
int main(void)
{
int list[NUM] = {35, 47, 63, 25, 93, 16, 52};
int x;
printf("Unsorted List: ");
for (x = 0; x < NUM; x++)
printf("%d ", list[x]);
qsort(list, NUM, sizeof(int), comp);
printf("\n");
printf("Sorted List:
");
for (x = 0; x < NUM; x++)
printf("%d ", list[x]);
}
int comp(const void *e1, const void *e2)
{
const int * a1 = e1;
const int * a2 = e2;
if (*a1 < *a2)
return -1;
else if (*a1 == *a2)
return 0;
else
return 1;
}
DS50001456J-page 114
 2004-2014 Microchip Technology Inc.
Standard C Libraries
qsort (Continued)
Output:
Unsorted List: 35
Sorted List:
16
47
25
63
35
25
47
93
52
16
63
52
93
rand
Description:
Generates a pseudo-random integer.
Include:
<stdlib.h>
Prototype:
int rand(void);
Return Value:
Returns an integer between 0 and RAND_MAX.
Remarks:
Calls to this function return pseudo-random integer values in the range
[0,RAND_MAX]. To use this function effectively, you must seed the random number generator using the srand function. This function will
always return the same sequence of integers when no seeds are used
(as in the example below) or when identical seed values are used. (See
srand for seed example.)
Example:
#include <stdio.h> /* for printf */
#include <stdlib.h> /* for rand
*/
int main(void)
{
int x;
for (x = 0; x < 5; x++)
printf("Number = %d\n", rand());
}
Output:
Number
Number
Number
Number
Number
=
=
=
=
=
21422
2061
16443
11617
9125
Notice if the program is run a second time, the numbers are the same.
See the example for srand to seed the random number generator.
realloc
Description:
Reallocates memory to allow a size change.
Include:
<stdlib.h>
Prototype:
void *realloc(void *ptr, size_t size);
Arguments:
ptr
points to previously allocated memory
size
new size to allocate to
Return Value:
Returns a pointer to the allocated space if successful; otherwise,
returns a null pointer. This function requires a heap.
Remarks:
If the existing object is smaller than the new object, the entire existing
object is copied to the new object and the remainder of the new object
is indeterminate. If the existing object is larger than the new object, the
function copies as much of the existing object as will fit in the new
object. If realloc succeeds in allocating a new object, the existing
object will be deallocated; otherwise, the existing object is left
unchanged. Keep a temporary pointer to the existing object since
realloc will return a null pointer on failure.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 115
16-Bit Language Tools Libraries
realloc (Continued)
Example:
#include <stdio.h> /* for printf, sizeof, NULL */
#include <stdlib.h> /* for realloc, malloc, free */
int main(void)
{
long *i, *j;
if ((i = (long *)malloc(50 * sizeof(long)))
== NULL)
printf("Cannot allocate memory\n");
else
{
printf("Memory allocated\n");
/* Temp pointer in case realloc() fails */
j = i;
if ((i = (long *)realloc(i, 25 * sizeof(long)))
== NULL)
{
printf("Cannot reallocate memory\n");
/* j pointed to allocated memory */
free(j);
}
else
{
printf("Memory reallocated\n");
free(i);
}
}
}
Output:
Memory allocated
Memory reallocated
DS50001456J-page 116
 2004-2014 Microchip Technology Inc.
Standard C Libraries
srand
Description:
Set the starting seed for the pseudo-random number sequence.
Include:
<stdlib.h>
Prototype:
void srand(unsigned int seed);
Argument:
seed
Return Value:
None.
Remarks:
This function sets the starting seed for the pseudo-random number
sequence generated by the rand function. The rand function will
always return the same sequence of integers when identical seed values are used. If rand is called with a seed value of 1, the sequence of
numbers generated will be the same as if rand had been called without
srand having been called first.
Example:
#include <stdio.h> /* for printf
*/
#include <stdlib.h> /* for rand, srand */
starting value for the pseudo-random number sequence
int main(void)
{
int x;
srand(7);
for (x = 0; x < 5; x++)
printf("Number = %d\n", rand());
}
Output:
Number
Number
Number
Number
Number
=
=
=
=
=
16327
5931
23117
30985
29612
strdup
Description:
Duplicates a string.
Include:
<stdlib.h>
Prototype:
char *strdup(const char *s1);
Arguments:
s1
Return Value:
A pointer to a new string on success. Otherwise, it shall return a null
pointer.
Remarks:
The strdup() function shall return a pointer to a new string, which is a
duplicate of the string pointed to by s1. The returned pointer can be
passed to free(). A null pointer is returned if the new string cannot be
created.
This function required a heap.
Example:
#include <stdio.h> /* for printf */
#include <stdlib.h> /* for strdup */
pointer to the string
int main(void)
{
char a[] = "MyString";
char *b;
 2004-2014 Microchip Technology Inc.
DS50001456J-page 117
16-Bit Language Tools Libraries
strdup (Continued)
b = strdup(a);
printf("String a = \"%s\"\n" , a );
printf("String b = \"%s\"\n" , b );
Output:
String a = "MyString"
String b = "MyString"
strtod
Description:
Converts a partial string to a floating-point number of type double.
Include:
<stdlib.h>
Prototype:
double strtod(const char *s, char **endptr);
Arguments:
s
string to be converted
endptr
pointer to the character at which the conversion stopped
Return Value:
Returns the converted number if successful; otherwise, returns 0.
Remarks:
The number may consist of the following:
[whitespace] [sign] digits [.digits]
[ { e | E }[sign]digits]
optional whitespace followed by an optional sign, then a sequence
of one or more digits with an optional decimal point, followed by one
or more optional digits and an optional e or E followed by an optional
signed exponent.
strtod converts the string until it reaches a character that cannot be
converted to a number. endptr will point to the remainder of the string
starting with the first unconverted character.
If a range error occurs, errno will be set.
Example:
#include <stdio.h> /* for printf */
#include <stdlib.h> /* for strtod */
int main(void)
{
char *end;
char a[] = "1.28 inches";
char b[] = "27.835e2i";
char c[] = "Number1";
double x;
x = strtod(a, &end);
printf("String = \"%s\" float = %f\n", a, x );
printf("Stopped at: %s\n\n", end );
x = strtod(b, &end);
printf("String = \"%s\" float = %f\n", b, x );
printf("Stopped at: %s\n\n", end );
x = strtod(c, &end);
printf("String = \"%s\"
float = %f\n", c, x );
printf("Stopped at: %s\n\n", end );
}
DS50001456J-page 118
 2004-2014 Microchip Technology Inc.
Standard C Libraries
strtod (Continued)
Output:
String = "1.28 inches"
Stopped at: inches
float = 1.280000
String = "27.835e2i" float = 2783.500000
Stopped at: i
String = "Number1"
Stopped at: Number1
float = 0.000000
strtol
Description:
Converts a partial string to a long integer.
Include:
<stdlib.h>
Prototype:
long strtol(const char *s, char **endptr, int base);
Arguments:
s
string to be converted
endptr
pointer to the character at which the conversion stopped
base
number base to use in conversion
Return Value:
Returns the converted number if successful; otherwise, returns 0.
Remarks:
If base is zero, strtol attempts to determine the base automatically.
It can be octal, determined by a leading zero; hexadecimal, determined
by a leading 0x or 0X; or decimal in any other case. If base is specified,
strtol converts a sequence of digits and letters a-z (case insensitive)
where a-z represents the numbers 10-36. Conversion stops when an
out of base number is encountered. endptr will point to the remainder
of the string starting with the first unconverted character. If a range
error occurs, errno will be set.
Example:
#include <stdio.h> /* for printf */
#include <stdlib.h> /* for strtol */
int main(void)
{
char *end;
char a[] = "-12BGEE";
char b[] = "1234Number";
long x;
x = strtol(a, &end, 16);
printf("String = \"%s\" long = %ld\n", a, x );
printf("Stopped at: %s\n\n", end );
x = strtol(b, &end, 4);
printf("String = \"%s\" long = %ld\n", b, x );
printf("Stopped at: %s\n\n", end );
}
Output:
String = "-12BGEE"
Stopped at: GEE
long = -299
String = "1234Number"
Stopped at: 4Number
 2004-2014 Microchip Technology Inc.
long = 27
DS50001456J-page 119
16-Bit Language Tools Libraries
strtoul
Description:
Converts a partial string to an unsigned long integer.
Include:
<stdlib.h>
Prototype:
unsigned long strtoul(const char *s, char **endptr,
int base);
Arguments:
s
string to be converted
endptr
pointer to the character at which the conversion stopped
base
number base to use in conversion
Return Value:
Returns the converted number if successful; otherwise, returns 0.
Remarks:
If base is zero, strtol attempts to determine the base automatically.
It can be octal, determined by a leading zero, hexadecimal, determined
by a leading 0x or 0X, or decimal in any other case. If base is specified
strtol converts a sequence of digits and letters a-z (case insensitive), where a-z represents the numbers 10-36. Conversion stops when
an out of base number is encountered. endptr will point to the remainder of the string starting with the first unconverted character. If a range
error occurs, errno will be set.
Example:
#include <stdio.h> /* for printf */
#include <stdlib.h> /* for strtoul */
int main(void)
{
char *end;
char a[] = "12BGET3";
char b[] = "0x1234Number";
char c[] = "-123abc";
unsigned long x;
x = strtoul(a, &end, 25);
printf("String = \"%s\" long = %lu\n", a, x );
printf("Stopped at: %s\n\n", end );
x = strtoul(b, &end, 0);
printf("String = \"%s\" long = %lu\n", b, x );
printf("Stopped at: %s\n\n", end );
x = strtoul(c, &end, 0);
printf("String = \"%s\" long = %lu\n", c, x );
printf("Stopped at: %s\n\n", end );
}
Output:
String = "12BGET3"
Stopped at: T3
long = 429164
String = "0x1234Number"
Stopped at: Number
String = "-123abc"
Stopped at: abc
DS50001456J-page 120
long = 4660
long = 4294967173
 2004-2014 Microchip Technology Inc.
Standard C Libraries
system
Description:
Execute a command.
Include:
<stdlib.h>
Prototype:
int system(const char *s);
Argument:
s
Remarks:
This function must be customized to be used as described (see
pic30-libs). By default, system will cause a Reset if called with
anything other than NULL. system(NULL) will do nothing.
Example:
/* This program uses system */
/* to TYPE its source file. */
command to be executed
#include <stdlib.h> /* for system */
int main(void)
{
system("type sampsystem.c");
}
Output:
System(type sampsystem.c) called: Aborting
wctomb
Description:
Converts a wide character to a multibyte character. (See Remarks.)
Include:
<stdlib.h>
Prototype:
int wctomb(char *s, wchar_t wchar);
Arguments:
s
points to the multibyte character
wchar
the wide character to be converted
Return Value:
Returns zero if s points to a null character; otherwise, returns 1.
Remarks:
The resulting multibyte character is stored at s. The 16-bit compiler
does not support multibyte characters with length greater than
1 character.
wcstombs
Description:
Converts a wide character string to a multibyte string. (See Remarks.)
Include:
<stdlib.h>
Prototype:
size_t wcstombs(char *s, const wchar_t *wcs,
size_t n);
Arguments:
s
points to the multibyte string
wcs
points to the wide character string
n
the number of characters to convert
Return Value:
Returns the number of characters stored excluding the null character.
Remarks:
wcstombs converts n number of multibyte characters unless it
encounters a null character first. The 16-bit compiler does not support
multibyte characters with length greater than 1 character.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 121
16-Bit Language Tools Libraries
2.15
<STRING.H> STRING FUNCTIONS
The header file, string.h, consists of types, macros and functions that provide tools
to manipulate strings.
size_t
Description:
The type of the result of the sizeof operator.
Include:
<string.h>
NULL
Description:
The value of a null pointer constant.
Include:
<string.h>
memchr
Description:
Locates a character in a buffer.
Include:
<string.h>
Prototype:
void *memchr(const void *s, int c, size_t n);
Arguments:
s
pointer to the buffer
c
character to search for
n
number of characters to check
Return Value:
Returns a pointer to the location of the match if successful; otherwise,
returns null.
Remarks:
memchr stops when it finds the first occurrence of c, or after searching
n number of characters.
Example:
#include <string.h> /* for memchr, NULL */
#include <stdio.h> /* for printf
*/
int main(void)
{
char buf1[50] = "What time is it?";
char ch1 = 'i', ch2 = 'y';
char *ptr;
int res;
printf("buf1 : %s\n\n", buf1);
ptr = memchr(buf1, ch1, 50);
if (ptr != NULL)
{
res = ptr - buf1 + 1;
printf("%c found at position %d\n", ch1, res);
}
else
printf("%c not found\n", ch1);
DS50001456J-page 122
 2004-2014 Microchip Technology Inc.
Standard C Libraries
memchr (Continued)
printf("\n");
ptr = memchr(buf1, ch2, 50);
if (ptr != NULL)
{
res = ptr - buf1 + 1;
printf("%c found at position %d\n", ch2, res);
}
else
printf("%c not found\n", ch2);
}
Output:
buf1 : What time is it?
i found at position 7
y not found
memcmp
Description:
Compare the contents of two buffers.
Include:
<string.h>
Prototype:
int memcmp(const void *s1, const void *s2, size_t n);
Arguments:
s1
first buffer
s2
second buffer
n
number of characters to compare
Return Value:
Returns a positive number if s1 is greater than s2, zero if s1 is equal to
s2 or a negative number if s1 is less than s2.
Remarks:
This function compares the first n characters in s1 to the first n characters in s2 and returns a value indicating whether the buffers are less
than, equal to or greater than each other.
Example:
#include <string.h> /* memcmp
*/
#include <stdio.h> /* for printf */
int main(void)
{
char buf1[50] = "Where is the time?";
char buf2[50] = "Where did they go?";
char buf3[50] = "Why?";
int res;
printf("buf1 : %s\n", buf1);
printf("buf2 : %s\n", buf2);
printf("buf3 : %s\n\n", buf3);
res = memcmp(buf1, buf2, 6);
if (res < 0)
printf("buf1 comes before buf2\n");
else if (res == 0)
printf("6 characters of buf1 and buf2 "
"are equal\n");
else
printf("buf2 comes before buf1\n");
 2004-2014 Microchip Technology Inc.
DS50001456J-page 123
16-Bit Language Tools Libraries
memcmp (Continued)
printf("\n");
res = memcmp(buf1, buf2, 20);
if (res < 0)
printf("buf1 comes before buf2\n");
else if (res == 0)
printf("20 characters of buf1 and buf2 "
"are equal\n");
else
printf("buf2 comes before buf1\n");
printf("\n");
res = memcmp(buf1, buf3, 20);
if (res < 0)
printf("buf1 comes before buf3\n");
else if (res == 0)
printf("20 characters of buf1 and buf3 "
"are equal\n");
else
printf("buf3 comes before buf1\n");
}
Output:
buf1 : Where is the time?
buf2 : Where did they go?
buf3 : Why?
6 characters of buf1 and buf2 are equal
buf2 comes before buf1
buf1 comes before buf3
DS50001456J-page 124
 2004-2014 Microchip Technology Inc.
Standard C Libraries
memcpy
Description:
Copies characters from one buffer to another.
Include:
<string.h>
Prototype:
void *memcpy(void *dst , const void *src , size_t n);
Arguments:
dst
buffer to copy characters to
src
buffer to copy characters from
n
number of characters to copy
Return Value:
Returns dst.
Remarks:
memcpy copies n characters from the source buffer src to the
destination buffer dst. If the buffers overlap, the behavior is undefined.
Example:
#include <string.h> /* memcpy
*/
#include <stdio.h> /* for printf */
int main(void)
{
char buf1[50] = "";
char buf2[50] = "Where is the time?";
char buf3[50] = "Why?";
printf("buf1 : %s\n", buf1);
printf("buf2 : %s\n", buf2);
printf("buf3 : %s\n\n", buf3);
memcpy(buf1, buf2, 6);
printf("buf1 after memcpy of 6 chars of "
"buf2: \n\t%s\n", buf1);
printf("\n");
memcpy(buf1, buf3, 5);
printf("buf1 after memcpy of 5 chars of "
"buf3: \n\t%s\n", buf1);
}
Output:
buf1 :
buf2 : Where is the time?
buf3 : Why?
buf1 after memcpy of 6 chars of buf2:
Where
buf1 after memcpy of 5 chars of buf3:
Why?
 2004-2014 Microchip Technology Inc.
DS50001456J-page 125
16-Bit Language Tools Libraries
memmove
Description:
Copies n characters of the source buffer into the destination buffer,
even if the regions overlap.
Include:
<string.h>
Prototype:
void *memmove(void *s1, const void *s2, size_t n);
Arguments:
s1
buffer to copy characters to (destination)
s2
buffer to copy characters from (source)
n
number of characters to copy from s2 to s1
Return Value:
Returns a pointer to the destination buffer.
Remarks:
If the buffers overlap, the effect is as if the characters are read first from
s2, then written to s1, so the buffer is not corrupted.
Example:
#include <string.h> /* for memmove */
#include <stdio.h> /* for printf */
int main(void)
{
char buf1[50] = "When time marches on";
char buf2[50] = "Where is the time?";
char buf3[50] = "Why?";
printf("buf1 : %s\n", buf1);
printf("buf2 : %s\n", buf2);
printf("buf3 : %s\n\n", buf3);
memmove(buf1, buf2, 6);
printf("buf1 after memmove of 6 chars of "
"buf2: \n\t%s\n", buf1);
printf("\n");
memmove(buf1, buf3, 5);
printf("buf1 after memmove of 5 chars of "
"buf3: \n\t%s\n", buf1);
}
Output:
buf1 : When time marches on
buf2 : Where is the time?
buf3 : Why?
buf1 after memmove of 6 chars of buf2:
Where ime marches on
buf1 after memmove of 5 chars of buf3:
Why?
DS50001456J-page 126
 2004-2014 Microchip Technology Inc.
Standard C Libraries
memset
Description:
Copies the specified character into the destination buffer.
Include:
<string.h>
Prototype:
void *memset(void *s, int c, size_t n);
Arguments:
s
buffer
c
character to put in buffer
n
number of times
Return Value:
Returns the buffer with characters written to it.
Remarks:
The character c is written to the buffer n times.
Example:
#include <string.h> /* for memset */
#include <stdio.h> /* for printf */
int main(void)
{
char buf1[20] = "What time is it?";
char buf2[20] = "";
char ch1 = '?', ch2 = 'y';
char *ptr;
int res;
printf("memset(\"%s\", \'%c\',4);\n", buf1, ch1);
memset(buf1, ch1, 4);
printf("buf1 after memset: %s\n", buf1);
printf("\n");
printf("memset(\"%s\", \'%c\',10);\n", buf2, ch2);
memset(buf2, ch2, 10);
printf("buf2 after memset: %s\n", buf2);
}
Output:
memset("What time is it?", '?',4);
buf1 after memset: ???? time is it?
memset("", 'y',10);
buf2 after memset: yyyyyyyyyy
 2004-2014 Microchip Technology Inc.
DS50001456J-page 127
16-Bit Language Tools Libraries
strcat
Description:
Appends a copy of the source string to the end of the destination string.
Include:
<string.h>
Prototype:
char *strcat(char *s1, const char *s2);
Arguments:
s1
null terminated destination string to copy to
s2
null terminated source string to be copied
Return Value:
Returns a pointer to the destination string.
Remarks:
This function appends the source string (including the terminating null
character) to the end of the destination string. The initial character of
the source string overwrites the null character at the end of the
destination string. If the buffers overlap, the behavior is undefined.
Example:
#include <string.h> /* for strcat, strlen */
#include <stdio.h> /* for printf
*/
int main(void)
{
char buf1[50] = "We're here";
char buf2[50] = "Where is the time?";
printf("buf1 : %s\n", buf1);
printf("\t(%d characters)\n\n", strlen(buf1));
printf("buf2 : %s\n", buf2);
printf("\t(%d characters)\n\n", strlen(buf2));
strcat(buf1, buf2);
printf("buf1 after strcat of buf2: \n\t%s\n",
buf1);
printf("\t(%d characters)\n", strlen(buf1));
printf("\n");
strcat(buf1, "Why?");
printf("buf1 after strcat of \"Why?\": \n\t%s\n",
buf1);
printf("\t(%d characters)\n", strlen(buf1));
}
Output:
buf1 : We're here
(10 characters)
buf2 : Where is the time?
(18 characters)
buf1 after strcat of buf2:
We're hereWhere is the time?
(28 characters)
buf1 after strcat of "Why?":
We're hereWhere is the time?Why?
(32 characters)
DS50001456J-page 128
 2004-2014 Microchip Technology Inc.
Standard C Libraries
strchr
Description:
Locates the first occurrence of a specified character in a string.
Include:
<string.h>
Prototype:
char *strchr(const char *s, int c);
Arguments:
s
pointer to the string
c
character to search for
Return Value:
Returns a pointer to the location of the match if successful; otherwise,
returns a null pointer.
Remarks:
This function searches the string s to find the first occurrence of the
character, c.
Example:
#include <string.h> /* for strchr, NULL */
#include <stdio.h> /* for printf
*/
int main(void)
{
char buf1[50] = "What time is it?";
char ch1 = 'm', ch2 = 'y';
char *ptr;
int res;
printf("buf1 : %s\n\n", buf1);
ptr = strchr(buf1, ch1);
if (ptr != NULL)
{
res = ptr - buf1 + 1;
printf("%c found at position %d\n", ch1, res);
}
else
printf("%c not found\n", ch1);
printf("\n");
ptr = strchr(buf1, ch2);
if (ptr != NULL)
{
res = ptr - buf1 + 1;
printf("%c found at position %d\n", ch2, res);
}
else
printf("%c not found\n", ch2);
}
Output:
buf1 : What time is it?
m found at position 8
y not found
 2004-2014 Microchip Technology Inc.
DS50001456J-page 129
16-Bit Language Tools Libraries
strcmp
Description:
Compares two strings.
Include:
<string.h>
Prototype:
int strcmp(const char *s1, const char *s2);
Arguments:
s1
first string
s2
second string
Return Value:
Returns a positive number if s1 is greater than s2, zero if s1 is equal to
s2 or a negative number if s1 is less than s2.
Remarks:
This function compares successive characters from s1 and s2 until
they are not equal or the null terminator is reached.
Example:
#include <string.h> /* for strcmp */
#include <stdio.h> /* for printf */
int main(void)
{
char buf1[50] = "Where is the time?";
char buf2[50] = "Where did they go?";
char buf3[50] = "Why?";
int res;
printf("buf1 : %s\n", buf1);
printf("buf2 : %s\n", buf2);
printf("buf3 : %s\n\n", buf3);
res = strcmp(buf1, buf2);
if (res < 0)
printf("buf1 comes before buf2\n");
else if (res == 0)
printf("buf1 and buf2 are equal\n");
else
printf("buf2 comes before buf1\n");
printf("\n");
res = strcmp(buf1, buf3);
if (res < 0)
printf("buf1 comes before buf3\n");
else if (res == 0)
printf("buf1 and buf3 are equal\n");
else
printf("buf3 comes before buf1\n");
printf("\n");
res = strcmp("Why?", buf3);
if (res < 0)
printf("\"Why?\" comes before buf3\n");
else if (res == 0)
printf("\"Why?\" and buf3 are equal\n");
else
printf("buf3 comes before \"Why?\"\n");
}
DS50001456J-page 130
 2004-2014 Microchip Technology Inc.
Standard C Libraries
strcmp (Continued)
Output:
buf1 : Where is the time?
buf2 : Where did they go?
buf3 : Why?
buf2 comes before buf1
buf1 comes before buf3
"Why?" and buf3 are equal
strcoll
Description:
Compares one string to another. (See Remarks.)
Include:
<string.h>
Prototype:
int strcoll(const char *s1, const char *s2);
Arguments:
s1
first string
s2
second string
Return Value:
Using the locale-dependent rules, it returns a positive number if s1 is
greater than s2, zero if s1 is equal to s2 or a negative number if s1 is
less than s2.
Remarks:
Since the 16-bit compiler does not support alternate locales, this
function is equivalent to strcmp.
strcpy
Description:
Copy the source string into the destination string.
Include:
<string.h>
Prototype:
char *strcpy(char *s1, const char *s2);
Arguments:
s1
destination string to copy to
s2
source string to copy from
Return Value:
Returns a pointer to the destination string.
Remarks:
All characters of s2 are copied, including the null terminating character.
If the strings overlap, the behavior is undefined.
Example:
#include <string.h> /* for strcpy, strlen */
#include <stdio.h> /* for printf
*/
int main(void)
{
char buf1[50] = "We're here";
char buf2[50] = "Where is the time?";
char buf3[50] = "Why?";
printf("buf1 : %s\n", buf1);
printf("buf2 : %s\n", buf2);
printf("buf3 : %s\n\n", buf3);
strcpy(buf1, buf2);
printf("buf1 after strcpy of buf2: \n\t%s\n\n",
buf1);
 2004-2014 Microchip Technology Inc.
DS50001456J-page 131
16-Bit Language Tools Libraries
strcpy (Continued)
strcpy(buf1, buf3);
printf("buf1 after strcpy of buf3: \n\t%s\n",
buf1);
}
Output:
buf1 : We're here
buf2 : Where is the time?
buf3 : Why?
buf1 after strcpy of buf2:
Where is the time?
buf1 after strcpy of buf3:
Why?
strcspn
Description:
Calculate the number of consecutive characters at the beginning of a
string that are not contained in a set of characters.
Include:
<string.h>
Prototype:
size_t strcspn(const char *s1, const char *s2);
Arguments:
s1
pointer to the string to be searched
s2
pointer to characters to search for
Return Value:
Returns the length of the segment in s1 not containing characters
found in s2.
Remarks:
This function will determine the number of consecutive characters from
the beginning of s1 that are not contained in s2.
Example:
#include <string.h> /* for strcspn */
#include <stdio.h> /* for printf */
int main(void)
{
char str1[20]
char str2[20]
char str3[20]
char str4[20]
int res;
=
=
=
=
"hello";
"aeiou";
"animal";
"xyz";
res = strcspn(str1, str2);
printf("strcspn(\"%s\", \"%s\") = %d\n",
str1, str2, res);
res = strcspn(str3, str2);
printf("strcspn(\"%s\", \"%s\") = %d\n",
str3, str2, res);
res = strcspn(str3, str4);
printf("strcspn(\"%s\", \"%s\") = %d\n",
str3, str4, res);
}
Output:
strcspn("hello", "aeiou") = 1
strcspn("animal", "aeiou") = 0
strcspn("animal", "xyz") = 6
DS50001456J-page 132
 2004-2014 Microchip Technology Inc.
Standard C Libraries
strcspn (Continued)
Explanation:
In the first result, e is in s2 so it stops counting after h.
In the second result, a is in s2.
In the third result, none of the characters of s1 are in s2 so all
characters are counted.
strerror
Description:
Gets an internal error message.
Include:
<string.h>
Prototype:
char *strerror(int errcode);
Argument:
errcode
Return Value:
Returns a pointer to an internal error message string corresponding to
the specified error code errcode.
Remarks:
The array pointed to by strerror may be overwritten by a
subsequent call to this function.
Example:
#include <stdio.h>
number of the error code
/*
/*
#include <string.h> /*
#include <errno.h> /*
for fopen, fclose,
printf, FILE, NULL
for strerror
for errno
*/
*/
*/
*/
int main(void)
{
FILE *myfile;
if ((myfile = fopen("samp.fil", "r+")) == NULL)
printf("Cannot open samp.fil: %s\n",
strerror(errno));
else
printf("Success opening samp.fil\n");
fclose(myfile);
}
Output:
Cannot open samp.fil: file open error
strlen
Description:
Finds the length of a string.
Include:
<string.h>
Prototype:
size_t strlen(const char *s);
Argument:
s
Return Value:
Returns the length of a string.
Remarks:
This function determines the length of the string, not including the
terminating null character.
 2004-2014 Microchip Technology Inc.
the string
DS50001456J-page 133
16-Bit Language Tools Libraries
strlen (Continued)
Example:
#include <string.h> /* for strlen */
#include <stdio.h> /* for printf */
int main(void)
{
char str1[20] = "We are here";
char str2[20] = "";
char str3[20] = "Why me?";
printf("str1 : %s\n", str1);
printf("\t(string length = %d characters)\n\n",
strlen(str1));
printf("str2 : %s\n", str2);
printf("\t(string length = %d characters)\n\n",
strlen(str2));
printf("str3 : %s\n", str3);
printf("\t(string length = %d characters)\n\n\n",
strlen(str3));
}
Output:
str1 : We are here
(string length = 11 characters)
str2 :
(string length = 0 characters)
str3 : Why me?
(string length = 7 characters)
strncat
Description:
Append a specified number of characters from the source string to the
destination string.
Include:
<string.h>
Prototype:
char *strncat(char *s1, const char *s2, size_t n);
Arguments:
s1
destination string to copy to
s2
source string to copy from
n
number of characters to append
Return Value:
Returns a pointer to the destination string.
Remarks:
This function appends up to n characters (a null character and characters that follow it are not appended) from the source string to the end of
the destination string. If a null character is not encountered, then a terminating null character is appended to the result. If the strings overlap,
the behavior is undefined.
Example:
#include <string.h> /* for strncat, strlen */
#include <stdio.h> /* for printf
*/
int main(void)
{
char buf1[50] = "We're here";
char buf2[50] = "Where is the time?";
char buf3[50] = "Why?";
DS50001456J-page 134
 2004-2014 Microchip Technology Inc.
Standard C Libraries
strncat (Continued)
printf("buf1 : %s\n", buf1);
printf("\t(%d characters)\n\n", strlen(buf1));
printf("buf2 : %s\n", buf2);
printf("\t(%d characters)\n\n", strlen(buf2));
printf("buf3 : %s\n", buf3);
printf("\t(%d characters)\n\n\n", strlen(buf3));
strncat(buf1, buf2, 6);
printf("buf1 after strncat of 6 characters "
"of buf2: \n\t%s\n", buf1);
printf("\t(%d characters)\n", strlen(buf1));
printf("\n");
strncat(buf1, buf2, 25);
printf("buf1 after strncat of 25 characters "
"of buf2: \n\t%s\n", buf1);
printf("\t(%d characters)\n", strlen(buf1));
printf("\n");
strncat(buf1, buf3, 4);
printf("buf1 after strncat of 4 characters "
"of buf3: \n\t%s\n", buf1);
printf("\t(%d characters)\n", strlen(buf1));
}
Output:
buf1 : We’re here
(10 characters)
buf2 : Where is the time?
(18 characters)
buf3 : Why?
(4 characters)
buf1 after strncat of 6 characters of buf2:
We’re hereWhere
(16 characters)
buf1 after strncat of 25 characters of buf2:
We’re hereWhere Where is the time?
(34 characters)
buf1 after strncat of 4 characters of buf3:
We’re hereWhere Where is the time?Why?
(38 characters)
 2004-2014 Microchip Technology Inc.
DS50001456J-page 135
16-Bit Language Tools Libraries
strncmp
Description:
Compare two strings, up to a specified number of characters.
Include:
<string.h>
Prototype:
int strncmp(const char *s1, const char *s2,
size_t n);
Arguments:
s1
first string
s2
second string
n
number of characters to compare
Return Value:
Returns a positive number if s1 is greater than s2, zero if s1 is equal to
s2 or a negative number if s1 is less than s2.
Remarks:
strncmp returns a value based on the first character that differs
between s1 and s2. Characters that follow a null character are not
compared.
Example:
#include <string.h> /* for strncmp */
#include <stdio.h> /* for printf */
int main(void)
{
char buf1[50] = "Where is the time?";
char buf2[50] = "Where did they go?";
char buf3[50] = "Why?";
int res;
printf("buf1 : %s\n", buf1);
printf("buf2 : %s\n", buf2);
printf("buf3 : %s\n\n", buf3);
res = strncmp(buf1, buf2, 6);
if (res < 0)
printf("buf1 comes before buf2\n");
else if (res == 0)
printf("6 characters of buf1 and buf2 "
"are equal\n");
else
printf("buf2 comes before buf1\n");
printf("\n");
res = strncmp(buf1, buf2, 20);
if (res < 0)
printf("buf1 comes before buf2\n");
else if (res == 0)
printf("20 characters of buf1 and buf2 "
"are equal\n");
else
printf("buf2 comes before buf1\n");
DS50001456J-page 136
 2004-2014 Microchip Technology Inc.
Standard C Libraries
strncmp (Continued)
printf("\n");
res = strncmp(buf1, buf3, 20);
if (res < 0)
printf("buf1 comes before buf3\n");
else if (res == 0)
printf("20 characters of buf1 and buf3 "
"are equal\n");
else
printf("buf3 comes before buf1\n");
}
Output:
buf1 : Where is the time?
buf2 : Where did they go?
buf3 : Why?
6 characters of buf1 and buf2 are equal
buf2 comes before buf1
buf1 comes before buf3
strncpy
Description:
Copy characters from the source string into the destination string, up to
the specified number of characters.
Include:
<string.h>
Prototype:
char *strncpy(char *s1, const char *s2, size_t n);
Arguments:
s1
destination string to copy to
s2
source string to copy from
n
number of characters to copy
Return Value:
Returns a pointer to the destination string.
Remarks:
Copies n characters from the source string to the destination string. If
the source string is less than n characters, the destination is filled with
null characters to total n characters. If n characters were copied and no
null character was found, then the destination string will not be
null-terminated. If the strings overlap, the behavior is undefined.
Example:
#include <string.h> /* for strncpy, strlen */
#include <stdio.h> /* for printf
*/
int main(void)
{
char buf1[50]
char buf2[50]
char buf3[50]
char buf4[7]
printf("buf1
printf("buf2
printf("buf3
printf("buf4
 2004-2014 Microchip Technology Inc.
=
=
=
=
:
:
:
:
"We're here";
"Where is the time?";
"Why?";
"Where?";
%s\n",
%s\n",
%s\n",
%s\n",
buf1);
buf2);
buf3);
buf4);
DS50001456J-page 137
16-Bit Language Tools Libraries
strncpy (Continued)
strncpy(buf1, buf2, 6);
printf("buf1 after strncpy of 6 characters "
"of buf2: \n\t%s\n", buf1);
printf("\t( %d characters)\n", strlen(buf1));
printf("\n");
strncpy(buf1, buf2, 18);
printf("buf1 after strncpy of 18 characters "
"of buf2: \n\t%s\n", buf1);
printf("\t( %d characters)\n", strlen(buf1));
printf("\n");
strncpy(buf1, buf3, 5);
printf("buf1 after strncpy of 5 characters "
"of buf3: \n\t%s\n", buf1);
printf("\t( %d characters)\n", strlen(buf1));
printf("\n");
strncpy(buf1, buf4, 9);
printf("buf1 after strncpy of 9 characters "
"of buf4: \n\t%s\n", buf1);
printf("\t( %d characters)\n", strlen(buf1));
}
Output:
buf1 : We’re here
buf2 : Where is the time?
buf3 : Why?
buf4 : Where?
buf1 after strncpy of 6 characters of buf2:
Where here
( 10 characters)
buf1 after strncpy of 18 characters of buf2:
Where is the time?
( 18 characters)
buf1 after strncpy of 5 characters of buf3:
Why?
( 4 characters)
buf1 after strncpy of 9 characters of buf4:
Where?
( 6 characters)
DS50001456J-page 138
 2004-2014 Microchip Technology Inc.
Standard C Libraries
strncpy (Continued)
Explanation:
Each buffer contains the string shown, followed by null characters for a
length of 50. Using strlen will find the length of the string up to, but
not including, the first null character.
In the first example, 6 characters of buf2 (“Where “) replace the first
6 characters of buf1 ("We’re ") and the rest of buf1 remains the same
("here" plus null characters).
In the second example, 18 characters replace the first 18 characters of
buf1 and the rest remain null characters.
In the third example, 5 characters of buf3 ("Why?" plus a null terminating character) replace the first 5 characters of buf1. buf1 now actually
contains ("Why?", 1 null character, " is the time?", 32 null characters).
strlen shows 4 characters because it stops when it reaches the first
null character.
In the fourth example, since buf4 is only 7 characters, strncpy uses
2 additional null characters to replace the first 9 characters of buf1. The
result of buf1 is 6 characters ("Where?") followed by 3 null characters,
followed by 9 characters ("the time?"), followed by 32 null characters.
strpbrk
Description:
Search a string for the first occurrence of a character from a specified
set of characters.
Include:
<string.h>
Prototype:
char *strpbrk(const char *s1, const char *s2);
Arguments:
s1
pointer to the string to be searched
s2
pointer to characters to search for
Return Value:
Returns a pointer to the matched character in s1 if found; otherwise,
returns a null pointer.
Remarks:
This function will search s1 for the first occurrence of a character
contained in s2.
Example:
#include <string.h> /* for strpbrk, NULL */
#include <stdio.h> /* for printf
*/
int main(void)
{
char str1[20] = "What time is it?";
char str2[20] = "xyz";
char str3[20] = "eou?";
char *ptr;
int res;
printf("strpbrk(\"%s\", \"%s\")\n", str1, str2);
ptr = strpbrk(str1, str2);
if (ptr != NULL)
{
res = ptr - str1 + 1;
printf("match found at position %d\n", res);
}
else
printf("match not found\n");
 2004-2014 Microchip Technology Inc.
DS50001456J-page 139
16-Bit Language Tools Libraries
strpbrk (Continued)
printf("\n");
printf("strpbrk(\"%s\", \"%s\")\n", str1, str3);
ptr = strpbrk(str1, str3);
if (ptr != NULL)
{
res = ptr - str1 + 1;
printf("match found at position %d\n", res);
}
else
printf("match not found\n");
}
Output:
strpbrk("What time is it?", "xyz")
match not found
strpbrk("What time is it?", "eou?")
match found at position 9
strrchr
Description:
Search for the last occurrence of a specified character in a string.
Include:
<string.h>
Prototype:
char *strrchr(const char *s, int c);
Arguments:
s
pointer to the string to be searched
c
character to search for
Return Value:
Returns a pointer to the character if found; otherwise, returns a null
pointer.
Remarks:
The function searches the string s, including the terminating null
character, to find the last occurrence of character c.
Example:
#include <string.h> /* for strrchr, NULL */
#include <stdio.h> /* for printf
*/
int main(void)
{
char buf1[50] = "What time is it?";
char ch1 = 'm', ch2 = 'y';
char *ptr;
int res;
printf("buf1 : %s\n\n", buf1);
ptr = strrchr(buf1, ch1);
if (ptr != NULL)
{
res = ptr - buf1 + 1;
printf("%c found at position %d\n", ch1, res);
}
else
printf("%c not found\n", ch1);
DS50001456J-page 140
 2004-2014 Microchip Technology Inc.
Standard C Libraries
strrchr (Continued)
printf("\n");
ptr = strrchr(buf1, ch2);
if (ptr != NULL)
{
res = ptr - buf1 + 1;
printf("%c found at position %d\n", ch2, res);
}
else
printf("%c not found\n", ch2);
}
Output:
buf1 : What time is it?
m found at position 8
y not found
strspn
Description:
Calculate the number of consecutive characters at the beginning of a
string that are contained in a set of characters.
Include:
<string.h>
Prototype:
size_t strspn(const char *s1, const char *s2);
Arguments:
s1
pointer to the string to be searched
s2
pointer to characters to search for
Return Value:
Returns the number of consecutive characters from the beginning of s1
that are contained in s2.
Remarks:
This function stops searching when a character from s1 is not in s2.
Example:
#include <string.h> /* for strspn */
#include <stdio.h> /* for printf */
int main(void)
{
char str1[20]
char str2[20]
char str3[20]
char str4[20]
int res;
=
=
=
=
"animal";
"aeiounm";
"aimnl";
"xyz";
res = strspn(str1, str2);
printf("strspn(\"%s\", \"%s\") = %d\n",
str1, str2, res);
res = strspn(str1, str3);
printf("strspn(\"%s\", \"%s\") = %d\n",
str1, str3, res);
res = strspn(str1, str4);
printf("strspn(\"%s\", \"%s\") = %d\n",
str1, str4, res);
}
 2004-2014 Microchip Technology Inc.
DS50001456J-page 141
16-Bit Language Tools Libraries
strspn (Continued)
Output:
strspn("animal", "aeiounm") = 5
strspn("animal", "aimnl") = 6
strspn("animal", "xyz") = 0
Explanation:
In the first result, l is not in s2.
In the second result, the terminating null is not in s2.
In the third result, a is not in s2 , so the comparison stops.
strstr
Description:
Search for the first occurrence of a string inside another string.
Include:
<string.h>
Prototype:
char *strstr(const char *s1, const char *s2);
Arguments:
s1
pointer to the string to be searched
s2
pointer to substring to be searched for
Return Value:
Returns the address of the first element that matches the substring if
found; otherwise, returns a null pointer.
Remarks:
This function will find the first occurrence of the string s2 (excluding the
null terminator) within the string s1. If s2 points to a zero length string,
s1 is returned.
Example:
#include <string.h> /* for strstr, NULL */
#include <stdio.h> /* for printf
*/
int main(void)
{
char str1[20] = "What time is it?";
char str2[20] = "is";
char str3[20] = "xyz";
char *ptr;
int res;
printf("str1 : %s\n", str1);
printf("str2 : %s\n", str2);
printf("str3 : %s\n\n", str3);
ptr = strstr(str1, str2);
if (ptr != NULL)
{
res = ptr - str1 + 1;
printf("\"%s\" found at position %d\n",
str2, res);
}
else
printf("\"%s\" not found\n", str2);
DS50001456J-page 142
 2004-2014 Microchip Technology Inc.
Standard C Libraries
strstr (Continued)
printf("\n");
ptr = strstr(str1, str3);
if (ptr != NULL)
{
res = ptr - str1 + 1;
printf("\"%s\" found at position %d\n",
str3, res);
}
else
printf("\"%s\" not found\n", str3);
}
Output:
str1 : What time is it?
str2 : is
str3 : xyz
"is" found at position 11
"xyz" not found
strtok
Description:
Break a string into substrings, or tokens, by inserting null characters in
place of specified delimiters.
Include:
<string.h>
Prototype:
char *strtok(char *s1, const char *s2);
Arguments:
s1
pointer to the null terminated string to be searched
s2
delimiters)
pointer to characters to be searched for (used as
Return Value:
Returns a pointer to the first character of a token (the first character in
s1 that does not appear in the set of characters of s2). If no token is
found, the null pointer is returned.
Remarks:
A sequence of calls to this function can be used to split up a string into
substrings (or tokens) by replacing specified characters with null characters. The first time this function is invoked on a particular string, that
string should be passed in s1. After the first time, this function can continue parsing the string from the last delimiter by invoking it with a null
value passed in s1.
It skips all leading characters that appear in the string s2 (delimiters),
then skips all characters not appearing in s2 (this segment of characters is the token), and then overwrites the next character with a null
character, terminating the current token. The function, strtok, then
saves a pointer to the character that follows, from which the next
search will start. If strtok finds the end of the string before it finds a
delimiter, the current token extends to the end of the string pointed to
by s1. If this is the first call to strtok, it does not modify the string (no
null characters are written to s1). The set of characters that is passed
in s2 need not be the same for each call to strtok.
If strtok is called with a non-null parameter for s1 after the initial call,
the string becomes the new string to search. The old string previously
searched will be lost.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 143
16-Bit Language Tools Libraries
strtok (Continued)
Example:
#include <string.h> /* for strtok, NULL */
#include <stdio.h> / * for printf
*/
int main(void)
{
char str1[30] = "Here, on top of the world!";
char delim[5] = ", .";
char *word;
int x;
printf("str1 : %s\n", str1);
x = 1;
word = strtok(str1,delim);
while (word != NULL)
{
printf("word %d: %s\n", x++, word);
word = strtok(NULL, delim);
}
}
Output:
str1 : Here, on top of the world!
word 1: Here
word 2: on
word 3: top
word 4: of
word 5: the
word 6: world!
strxfrm
DS50001456J-page 144
Description:
Transforms a string using the locale-dependent rules (see Remarks).
Include:
<string.h>
Prototype:
size_t strxfrm(char *s1, const char *s2, size_t n);
Arguments:
s1
destination string
s2
source string to be transformed
n
number of characters to transform
Return Value:
Returns the length of the transformed string not including the terminating null character. If n is zero, the string is not transformed (s1 may be
a point null in this case) and the length of s2 is returned.
Remarks:
If the return value is greater than or equal to n, the content of s1 is
indeterminate. Since the 16-bit compiler does not support alternate
locales, the transformation is equivalent to strcpy, except that the
length of the destination string is bounded by n-1.
 2004-2014 Microchip Technology Inc.
Standard C Libraries
2.16
<TIME.H> DATE AND TIME FUNCTIONS
The header file time.h consists of types, macros and functions that manipulate time.
clock_t
Description:
Stores processor time values.
Include:
<time.h>
Prototype:
typedef long clock_t
size_t
Description:
The type of the result of the sizeof operator.
Include:
<time.h>
struct tm
Description:
Structure used to hold the time and date (calendar time).
Include:
<time.h>
Prototype:
struct tm {
int tm_sec;/*seconds after the minute ( 0 to 61 )*/
/*allows for up to two leap seconds*/
int tm_min;/*minutes after the hour ( 0 to 59 )*/
int tm_hour;/*hours since midnight ( 0 to 23 )*/
int tm_mday;/*day of month ( 1 to 31 )*/
int tm_mon;/*month ( 0 to 11 where January = 0 )*/
int tm_year;/*years since 1900*/
int tm_wday;/*day of week ( 0 to 6 where Sunday = 0
)*/
int tm_yday;/*day of year ( 0 to 365 where January 1
= 0 )*/
int tm_isdst;/*Daylight Savings Time flag*/
}
Remarks:
If tm_isdst is a positive value, Daylight Savings is in effect. If it is
zero, Daylight Saving Time is not in effect. If it is a negative value, the
status of Daylight Saving Time is not known.
time_t
Description:
Represents calendar time values.
Include:
<time.h>
Prototype:
typedef long time_t
CLOCKS_PER_SEC
Description:
Number of processor clocks per second.
Include:
<time.h>
Prototype:
#define CLOCKS_PER_SEC
Value:
1
Remarks:
The compiler returns clock ticks (instruction cycles) not actual time.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 145
16-Bit Language Tools Libraries
NULL
Description:
The value of a null pointer constant.
Include:
<time.h>
asctime
Description:
Converts the time structure to a character string.
Include:
<time.h>
Prototype:
char *asctime(const struct tm *tptr);
Argument:
tptr
Return Value:
Returns a pointer to a character string of the following format:
DDD MMM dd hh:mm:ss YYYY
DDD is day of the week
MMM is month of the year
dd is day of the month
hh is hour
mm is minute
ss is second
YYYY is year
Example:
#include <time.h> /* for asctime, tm */
#include <stdio.h> /* for printf
*/
time/date structure
volatile int i;
int main(void)
{
struct tm when;
time_t whattime;
when.tm_sec = 30;
when.tm_min = 30;
when.tm_hour = 2;
when.tm_mday = 1;
when.tm_mon = 1;
when.tm_year = 103;
whattime = mktime(&when);
printf("Day and time is %s\n", asctime(&when));
}
Output:
Day and time is Sat Feb
1 02:30:30 2003
clock
DS50001456J-page 146
Description:
Calculates the processor time.
Include:
<time.h>
Prototype:
clock_t clock(void);
Return Value:
Returns the number of clock ticks of elapsed processor time.
Remarks:
If the target environment cannot measure elapsed processor time, the
function returns -1 cast as a clock_t (i.e. (clock_t) -1). By default,
the 16-bit compiler returns the time as instruction cycles.
 2004-2014 Microchip Technology Inc.
Standard C Libraries
clock (Continued)
Example:
#include <time.h> /* for clock */
#include <stdio.h> /* for printf */
volatile int i;
int main(void)
{
clock_t start, stop;
int ct;
start = clock();
for (i = 0; i < 10; i++)
stop = clock();
printf("start = %ld\n", start);
printf("stop = %ld\n", stop);
}
Output:
start = 0
stop = 317
ctime
Description:
Converts calendar time to a string representation of local time.
Include:
<time.h>
Prototype:
char *ctime(const time_t *tod);
Argument:
tod
Return Value:
Returns the address of a string that represents the local time of the
parameter passed.
Remarks:
This function is equivalent to asctime(localtime(tod)).
Example:
#include <time.h> /* for mktime, tm, ctime */
#include <stdio.h> /* for printf
*/
pointer to stored time
int main(void)
{
time_t whattime;
struct tm nowtime;
nowtime.tm_sec = 30;
nowtime.tm_min = 30;
nowtime.tm_hour = 2;
nowtime.tm_mday = 1;
nowtime.tm_mon = 1;
nowtime.tm_year = 103;
whattime = mktime(&nowtime);
printf("Day and time %s\n", ctime(&whattime));
}
Output:
Day and time Sat Feb
 2004-2014 Microchip Technology Inc.
1 02:30:30 2003
DS50001456J-page 147
16-Bit Language Tools Libraries
difftime
Description:
Find the difference between two times.
Include:
<time.h>
Prototype:
double difftime(time_t t1, time_t t0);
Arguments:
t1
ending time
t0
beginning time
Return Value:
Returns the number of seconds between t1 and t0.
Remarks:
By default, the 16-bit compiler returns the time as instruction cycles so
difftime returns the number of ticks between t1 and t0.
Example:
#include <time.h> /* for clock, difftime */
#include <stdio.h> /* for printf
*/
volatile int i;
int main(void)
{
clock_t start, stop;
double elapsed;
start = clock();
for (i = 0; i < 10; i++)
stop = clock();
printf("start = %ld\n", start);
printf("stop = %ld\n", stop);
elapsed = difftime(stop, start);
printf("Elapsed time = %.0f\n", elapsed);
}
Output:
start = 0
stop = 317
Elapsed time = 317
gmtime
DS50001456J-page 148
Description:
Converts calendar time to time structure expressed as Universal Time
Coordinated (UTC) also known as Greenwich Mean Time (GMT).
Include:
<time.h>
Prototype:
struct tm *gmtime(const time_t *tod);
Argument:
tod
Return Value:
Returns the address of the time structure.
Remarks:
This function breaks down the tod value into the time structure of type
tm. By default, the 16-bit compiler returns the time as instruction
cycles. With this default, gmtime and localtime will be equivalent,
except gmtime will return tm_isdst (Daylight Savings Time flag) as
zero to indicate that Daylight Savings Time is not in effect.
pointer to stored time
 2004-2014 Microchip Technology Inc.
Standard C Libraries
gmtime (Continued)
Example:
#include <time.h>
/* for gmtime, asctime, */
/* time_t, tm
*/
#include <stdio.h> /* for printf
*/
int main(void)
{
time_t timer;
struct tm *newtime;
timer = 1066668182; /* Mon Oct 20 16:43:02 2003 */
newtime = gmtime(&timer);
printf("UTC time = %s\n", asctime(newtime));
}
Output:
UTC time = Mon Oct 20 16:43:02 2003
localtime
Description:
Converts a value to the local time.
Include:
<time.h>
Prototype:
struct tm *localtime(const time_t *tod);
Argument:
tod
Return Value:
Returns the address of the time structure.
Remarks:
By default, the 16-bit compiler returns the time as instruction cycles.
With this default, localtime and gmtime will be equivalent, except
localtime will return tm_isdst (Daylight Savings Time flag) as -1 to
indicate that the status of Daylight Savings Time is not known.
Example:
#include <time.h>
pointer to stored time
/* for localtime,
*/
/* asctime, time_t, tm */
#include <stdio.h> /* for printf
*/
int main(void)
{
time_t timer;
struct tm *newtime;
timer = 1066668182; /* Mon Oct 20 16:43:02 2003 */
newtime = localtime(&timer);
printf("Local time = %s\n", asctime(newtime));
}
Output:
Local time = Mon Oct 20 16:43:02 2003
 2004-2014 Microchip Technology Inc.
DS50001456J-page 149
16-Bit Language Tools Libraries
mktime
Description:
Converts local time to a calendar value.
Include:
<time.h>
Prototype:
time_t mktime(struct tm *tptr);
Argument:
tptr
Return Value:
Returns the calendar time encoded as a value of time_t.
Remarks:
If the calendar time cannot be represented, the function returns -1 cast
as a time_t (i.e. (time_t) -1).
Example:
#include <time.h>
a pointer to the time structure
/*
/*
/*
#include <stdio.h> /*
for localtime,
asctime, mktime,
time_t, tm
for printf
*/
*/
*/
*/
int main(void)
{
time_t timer, whattime;
struct tm *newtime;
timer = 1066668182; /* Mon Oct 20 16:43:02 2003 */
/* localtime allocates space for struct tm */
newtime = localtime(&timer);
printf("Local time = %s", asctime(newtime));
whattime = mktime(newtime);
printf("Calendar time as time_t = %ld\n",
whattime);
}
Output:
Local time = Mon Oct 20 16:43:02 2003
Calendar time as time_t = 1066668182
strftime
Description:
Formats the time structure to a string based on the format parameter.
Include:
<time.h>
Prototype:
size_t strftime(char *s, size_t n,
const char *format, const struct tm *tptr);
Arguments:
s
output string
n
maximum length of string
format
format-control string
tptr
pointer to tm data structure
Return Value:
Returns the number of characters placed in the array, s, if the total,
including the terminating null, is not greater than n. Otherwise, the
function returns 0 and the contents of array s are indeterminate.
Remarks:
The format parameters follow:
%a abbreviated weekday name
%A full weekday name
%b abbreviated month name
%B full month name
%c appropriate date and time representation
%d day of the month (01-31)
%H hour of the day (00-23)
DS50001456J-page 150
 2004-2014 Microchip Technology Inc.
Standard C Libraries
strftime (Continued)
%I
hour of the day (01-12)
%j
day of the year (001-366)
%m month of the year (01-12)
%M minute of the hour (00-59)
%p
AM/PM designator
%S second of the minute (00-61)
allowing for up to two leap seconds
%U week number of the year where Sunday is the first day of week 1
(00-53)
%w weekday where Sunday is day 0 (0-6)
%W week number of the year where Monday is the first day of week 1
(00-53)
%x
appropriate date representation
%X appropriate time representation
%y
year without century (00-99)
%Y
year with century
%Z time zone (possibly abbreviated) or no characters if time zone is
unavailable
%% percent character %
Example:
#include <time.h>
/*
/*
/*
#include <stdio.h> /*
for strftime,
localtime,
time_t, tm
for printf
*/
*/
*/
*/
int main(void)
{
time_t timer, whattime;
struct tm *newtime;
char buf[128];
timer = 1066668182; /* Mon Oct 20 16:43:02 2003 */
/* localtime allocates space for structure */
newtime = localtime(&timer);
strftime(buf, 128, "It was a %A, %d days into the "
"month of %B in the year %Y.\n", newtime);
printf(buf);
strftime(buf, 128, "It was %W weeks into the year "
"or %j days into the year.\n", newtime);
printf(buf);
}
Output:
It was a Monday, 20 days into the month of October in
the year 2003.
It was 42 weeks into the year or 293 days into the
year.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 151
16-Bit Language Tools Libraries
time
Description:
Calculates the current calendar time.
Include:
<time.h>
Prototype:
time_t time(time_t *tod);
Argument:
tod
Return Value:
Returns the calendar time encoded as a value of time_t.
Remarks:
If the target environment cannot determine the time, the function
returns -1 cast as a time_t. By default, the 16-bit compiler returns the
time as instruction cycles. This function is customizable (see
pic30-libs).
Example:
#include <time.h> /* for time
*/
#include <stdio.h> /* for printf */
pointer to storage location for time
volatile int i;
int main(void)
{
time_t ticks;
time(0); /* start time */
for (i = 0; i < 10; i++) /* waste time */
time(&ticks); /* get time */
printf("Time = %ld\n", ticks);
}
Output:
Time = 256
DS50001456J-page 152
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16-BIT LANGUAGE TOOLS
LIBRARIES
Chapter 3. Standard C Libraries - Math Functions
3.1
INTRODUCTION
Standard ANSI C library math functions are contained in the file, libm-omf.a, where
omf will be coff or elf depending upon the selected object module format.
3.1.1
Assembly Code Applications
A free version of the math functions library and header file is available from the
Microchip web site. No source code is available with this free version.
3.1.2
C Code Applications
The MPLAB XC16 C Compiler install directory (Section 1.1.1 “Compiler Installation
Locations”) contains the following subdirectories with library-related files:
• lib – standard C library files
• src\libm – source code for math library functions, batch file to rebuild the library
• support\h – header files for libraries
In addition, there is a file, ResourceGraphs.pdf, which contains diagrams of resources
used by each function, located in lib.
3.1.3
Chapter Organization
This chapter is organized as follows:
• Using the Standard C Libraries
• <math.h> mathematical functions
3.2
USING THE STANDARD C LIBRARIES
Building an application which utilizes the standard C libraries requires two types of files:
header files and library files.
3.2.1
Header Files
All standard C library entities are declared or defined in one or more standard headers.
(See list in Section 3.1.3 “Chapter Organization”.) To make use of a library entity in
a program, write an include directive that names the relevant standard header.
The contents of a standard header are included by naming them in an include directive,
as in:
#include <stdio.h> /* include I/O facilities */
The standard headers can be included in any order. Do not include a standard header
within a declaration. Do not define macros that have the same names as keywords
before including a standard header.
A standard header never includes another standard header.
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3.2.2
Library Files
The archived library files contain all the individual object files for each library function.
When linking an application, the library file must be provided as an input to the linker
(using the --library or -l linker option), such that the functions used by the
application may be linked into the application.
A typical C application will require three library files: libc-omf.a, libm-omf.a and
libpic30-omf.a (see Section 1.2 “OMF-Specific Libraries/Start-up Modules” for
more on OMF-specific libraries). These libraries will be included automatically if linking
is performed using the compiler.
Note:
DS50001456J-page 154
Some standard library functions require a heap. These include the standard
I/O functions that open files and the memory allocation functions. See the
“MPLAB® XC16 Assembler, Linker and Utilities User’s Guide” (DS50002106)
and “MPLAB® XC16 C Compiler User’s Guide” (DS50002071) for more
information on the heap.
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Math Functions
3.3
<MATH.H> MATHEMATICAL FUNCTIONS
The header file math.h consists of a macro and various functions that calculate common mathematical operations. Error conditions may be handled with a domain error or
range error (see errno.h).
A domain error occurs when the input argument is outside the domain over which the
function is defined. The error is reported by storing the value of EDOM in errno and
returning a particular value defined for each function.
A range error occurs when the result is too large or too small to be represented in the
target precision. The error is reported by storing the value of ERANGE in errno and
returning HUGE_VAL if the result overflowed (return value was too large) or a zero if the
result underflowed (return value is too small).
Responses to special values, such as NaNs, zeros and infinities, may vary depending
upon the function. Each function description includes a definition of the function’s
response to such values.
HUGE_VAL
Description:
HUGE_VAL is returned by a function on a range error (e.g., the function
tries to return a value too large to be represented in the target
precision).
Include:
<math.h>
Remarks:
-HUGE_VAL is returned if a function result is negative and is too large
(in magnitude) to be represented in the target precision. When the
printed result is +/- HUGE_VAL, it will be represented by +/- inf.
acos
Description:
Calculates the trigonometric arc cosine function of a double precision
floating-point value.
Include:
<math.h>
Prototype:
double acos (double x);
Argument:
x
Return Value:
Returns the arc cosine in radians in the range of 0 to pi (inclusive).
Remarks:
A domain error occurs if x is less than -1 or greater than 1.
Example:
#include <math.h> /* for acos
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
value between -1 and 1 for which to return the arc cosine
int main(void)
{
double x,y;
errno = 0;
x = -2.0;
y = acos (x);
if (errno)
perror("Error");
printf("The arccosine of %f is %f\n\n", x, y);
 2004-2014 Microchip Technology Inc.
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acos (Continued)
errno = 0;
x = 0.10;
y = acos (x);
if (errno)
perror("Error");
printf("The arccosine of %f is %f\n\n", x, y);
}
Output:
Error: domain error
The arccosine of -2.000000 is nan
The arccosine of 0.100000 is 1.470629
acosf
Description:
Calculates the trigonometric arc cosine function of a single precision
floating-point value.
Include:
<math.h>
Prototype:
float acosf (float x);
Argument:
x
Return Value:
Returns the arc cosine in radians in the range of 0 to pi (inclusive).
Remarks:
A domain error occurs if x is less than -1 or greater than 1.
Example:
#include <math.h> /* for acosf
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
value between -1 and 1
int main(void)
{
float x, y;
errno = 0;
x = 2.0F;
y = acosf (x);
if (errno)
perror("Error");
printf("The arccosine of %f is %f\n\n", x, y);
errno = 0;
x = 0.0F;
y = acosf (x);
if (errno)
perror("Error");
printf("The arccosine of %f is %f\n", x, y);
}
Output:
Error: domain error
The arccosine of 2.000000 is nan
The arccosine of 0.000000 is 1.570796
DS50001456J-page 156
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Math Functions
asin
Description:
Calculates the trigonometric arc sine function of a double precision
floating-point value.
Include:
<math.h>
Prototype:
double asin (double x);
Argument:
x
Return Value:
Returns the arc sine in radians in the range of -pi/2 to +pi/2 (inclusive).
Remarks:
A domain error occurs if x is less than -1 or greater than 1.
Example:
#include <math.h> /* for asin
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
value between -1 and 1 for which to return the arc sine
int main(void)
{
double x, y;
errno = 0;
x = 2.0;
y = asin (x);
if (errno)
perror("Error");
printf("The arcsine of %f is %f\n\n", x, y);
errno = 0;
x = 0.0;
y = asin (x);
if (errno)
perror("Error");
printf("The arcsine of %f is %f\n\n", x, y);
}
Output:
Error: domain error
The arcsine of 2.000000 is nan
The arcsine of 0.000000 is 0.000000
asinf
Description:
Calculates the trigonometric arc sine function of a single precision
floating-point value.
Include:
<math.h>
Prototype:
float asinf (float x);
Argument:
x
Return Value:
Returns the arc sine in radians in the range of -pi/2 to +pi/2 (inclusive).
Remarks:
A domain error occurs if x is less than -1 or greater than 1.
Example:
#include <math.h> /* for asinf
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
value between -1 and 1
int main(void)
{
float x, y;
 2004-2014 Microchip Technology Inc.
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asinf (Continued)
errno = 0;
x = 2.0F;
y = asinf(x);
if (errno)
perror("Error");
printf("The arcsine of %f is %f\n\n", x, y);
errno = 0;
x = 0.0F;
y = asinf(x);
if (errno)
perror("Error");
printf("The arcsine of %f is %f\n\n", x, y);
}
Output:
Error: domain error
The arcsine of 2.000000 is nan
The arcsine of 0.000000 is 0.000000
atan
Description:
Calculates the trigonometric arc tangent function of a double precision
floating-point value.
Include:
<math.h>
Prototype:
double atan (double x);
Argument:
x
Return Value:
Returns the arc tangent in radians in the range of -pi/2 to +pi/2
(inclusive).
Remarks:
No domain or range error will occur.
Example:
#include <math.h> /* for atan
*/
#include <stdio.h> /* for printf */
value for which to return the arc tangent
int main(void)
{
double x, y;
x = 2.0;
y = atan (x);
printf("The arctangent of %f is %f\n\n", x, y);
x = -1.0;
y = atan (x);
printf("The arctangent of %f is %f\n\n", x, y);
}
Output:
The arctangent of 2.000000 is 1.107149
The arctangent of -1.000000 is -0.785398
DS50001456J-page 158
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Math Functions
atanf
Description:
Calculates the trigonometric arc tangent function of a single precision
floating-point value.
Include:
<math.h>
Prototype:
float atanf (float x);
Argument:
x
Return Value:
Returns the arc tangent in radians in the range of -pi/2 to +pi/2
(inclusive).
Remarks:
No domain or range error will occur.
Example:
#include <math.h> /* for atanf */
#include <stdio.h> /* for printf */
value for which to return the arc tangent
int main(void)
{
float x, y;
x = 2.0F;
y = atanf (x);
printf("The arctangent of %f is %f\n\n", x, y);
x = -1.0F;
y = atanf (x);
printf("The arctangent of %f is %f\n\n", x, y);
}
Output:
The arctangent of 2.000000 is 1.107149
The arctangent of -1.000000 is -0.785398
atan2
Description:
Calculates the trigonometric arc tangent function of y/x.
Include:
<math.h>
Prototype:
double atan2 (double y, double x);
Arguments:
y
y value for which to return the arc tangent
x
x value for which to return the arc tangent
Return Value:
Returns the arc tangent in radians in the range of -pi to pi (inclusive)
with the quadrant determined by the signs of both parameters.
Remarks:
A domain error occurs if both x and y are zero or both x and y are
+/- infinity.
Example:
#include <math.h> /* for atan2
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
int main(void)
{
double x, y, z;
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atan2 (Continued)
errno = 0;
x = 0.0;
y = 2.0;
z = atan2(y, x);
if (errno)
perror("Error");
printf("The arctangent of %f/%f is %f\n\n",
y, x, z);
errno = 0;
x = -1.0;
y = 0.0;
z = atan2(y, x);
if (errno)
perror("Error");
printf("The arctangent of %f/%f is %f\n\n",
y, x, z);
errno = 0;
x = 0.0;
y = 0.0;
z = atan2(y, x);
if (errno)
perror("Error");
printf("The arctangent of %f/%f is %f\n\n",
y, x, z);
}
Output:
The arctangent of 2.000000/0.000000 is 1.570796
The arctangent of 0.000000/-1.000000 is 3.141593
Error: domain error
The arctangent of 0.000000/0.000000 is nan
DS50001456J-page 160
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Math Functions
atan2f
Description:
Calculates the trigonometric arc tangent function of y/x.
Include:
<math.h>
Prototype:
float atan2f (float y, float x);
Arguments:
y
y value for which to return the arc tangent
x
x value for which to return the arc tangent
Return Value:
Returns the arc tangent in radians in the range of -pi to pi with the
quadrant determined by the signs of both parameters.
Remarks:
A domain error occurs if both x and y are zero or both x and y are
+/- infinity.
Example:
#include <math.h> /* for atan2f
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
int main(void)
{
float x, y, z;
errno = 0;
x = 2.0F;
y = 0.0F;
z = atan2f (y, x);
if (errno)
perror("Error");
printf("The arctangent of %f/%f is %f\n\n",
y, x, z);
errno = 0;
x = 0.0F;
y = -1.0F;
z = atan2f (y, x);
if (errno)
perror("Error");
printf("The arctangent of %f/%f is %f\n\n",
y, x, z);
errno = 0;
x = 0.0F;
y = 0.0F;
z = atan2f (y, x);
if (errno)
perror("Error");
printf("The arctangent of %f/%f is %f\n\n",
y, x, z);
}
Output:
The arctangent of 2.000000/0.000000 is 1.570796
The arctangent of 0.000000/-1.000000 is 3.141593
Error: domain error
The arctangent of 0.000000/0.000000 is nan
 2004-2014 Microchip Technology Inc.
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ceil
Description:
Calculates the ceiling of a value.
Include:
<math.h>
Prototype:
double ceil(double x);
Argument:
x
Return Value:
Returns the smallest integer value greater than or equal to x.
Remarks:
No domain or range error will occur. See floor.
Example:
#include <math.h> /* for ceil
*/
#include <stdio.h> /* for printf */
a floating-point value for which to return the ceiling
int main(void)
{
double x[8] = {2.0, 1.75, 1.5, 1.25, -2.0,
-1.75, -1.5, -1.25};
double y;
int i;
for (i=0; i<8; i++)
{
y = ceil (x[i]);
printf("The ceiling for
}
%f is
%f\n", x[i], y);
}
Output:
The ceiling
The ceiling
The ceiling
The ceiling
The ceiling
The ceiling
The ceiling
The ceiling
DS50001456J-page 162
for
for
for
for
for
for
for
for
2.000000 is
1.750000 is
1.500000 is
1.250000 is
-2.000000 is
-1.750000 is
-1.500000 is
-1.250000 is
2.000000
2.000000
2.000000
2.000000
-2.000000
-1.000000
-1.000000
-1.000000
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Math Functions
ceilf
Description:
Calculates the ceiling of a value.
Include:
<math.h>
Prototype:
float ceilf(float x);
Argument:
x
Return Value:
Returns the smallest integer value greater than or equal to x.
Remarks:
No domain or range error will occur (see floorf).
Example:
#include <math.h> /* for ceilf */
#include <stdio.h> /* for printf */
floating-point value
int main(void)
{
float x[8] = {2.0F, 1.75F, 1.5F, 1.25F,
-2.0F, -1.75F, -1.5F, -1.25F};
float y;
int i;
for (i=0; i<8; i++)
{
y = ceilf (x[i]);
printf("The ceiling for
}
%f is
%f\n", x[i], y);
}
Output:
The ceiling
The ceiling
The ceiling
The ceiling
The ceiling
The ceiling
The ceiling
The ceiling
for
for
for
for
for
for
for
for
2.000000 is
1.750000 is
1.500000 is
1.250000 is
-2.000000 is
-1.750000 is
-1.500000 is
-1.250000 is
2.000000
2.000000
2.000000
2.000000
-2.000000
-1.000000
-1.000000
-1.000000
cos
Description:
Calculates the trigonometric cosine function of a double precision
floating-point value.
Include:
<math.h>
Prototype:
double cos (double x);
Argument:
x
Return Value:
Returns the cosine of x in radians in the ranges of -1 to 1 inclusive.
Remarks:
A domain error will occur if x is a NaN or infinity.
Example:
#include <math.h> /* for cos
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
value for which to return the cosine
int main(void)
{
double x,y;
 2004-2014 Microchip Technology Inc.
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cos (Continued)
errno = 0;
x = -1.0;
y = cos (x);
if (errno)
perror("Error");
printf("The cosine of %f is %f\n\n", x, y);
errno = 0;
x = 0.0;
y = cos (x);
if (errno)
perror("Error");
printf("The cosine of %f is %f\n\n", x, y);
}
Output:
The cosine of -1.000000 is 0.540302
The cosine of 0.000000 is 1.000000
cosf
Description:
Calculates the trigonometric cosine function of a single precision
floating-point value.
Include:
<math.h>
Prototype:
float cosf (float x);
Argument:
x
Return Value:
Returns the cosine of x in radians in the ranges of -1 to 1 inclusive.
Remarks:
A domain error will occur if x is a NaN or infinity.
Example:
#include <math.h> /* for cosf
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
value for which to return the cosine
int main(void)
{
float x, y;
errno = 0;
x = -1.0F;
y = cosf (x);
if (errno)
perror("Error");
printf("The cosine of %f is %f\n\n", x, y);
errno = 0;
x = 0.0F;
y = cosf (x);
if (errno)
perror("Error");
printf("The cosine of %f is %f\n\n", x, y);
}
DS50001456J-page 164
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Math Functions
cosf (Continued)
Output:
The cosine of -1.000000 is 0.540302
The cosine of 0.000000 is 1.000000
cosh
Description:
Calculates the hyperbolic cosine function of a double precision
floating-point value.
Include:
<math.h>
Prototype:
double cosh (double x);
Argument:
x
Return Value:
Returns the hyperbolic cosine of x.
Remarks:
A range error will occur if the magnitude of x is too large.
Example:
#include <math.h> /* for cosh
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
value for which to return the hyperbolic cosine
int main(void)
{
double x, y;
errno = 0;
x = -1.5;
y = cosh (x);
if (errno)
perror("Error");
printf("The hyperbolic cosine of %f is %f\n\n",
x, y);
errno = 0;
x = 0.0;
y = cosh (x);
if (errno)
perror("Error");
printf("The hyperbolic cosine of %f is %f\n\n",
x, y);
errno = 0;
x = 720.0;
y = cosh (x);
if (errno)
perror("Error");
printf("The hyperbolic cosine of %f is %f\n\n",
x, y);
}
Output:
The hyperbolic cosine of -1.500000 is 2.352410
The hyperbolic cosine of 0.000000 is 1.000000
Error: range error
The hyperbolic cosine of 720.000000 is inf
 2004-2014 Microchip Technology Inc.
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16-Bit Language Tools Libraries
coshf
Description:
Calculates the hyperbolic cosine function of a single precision
floating-point value.
Include:
<math.h>
Prototype:
float coshf (float x);
Argument:
x
Return Value:
Returns the hyperbolic cosine of x.
Remarks:
A range error will occur if the magnitude of x is too large.
Example:
#include <math.h> /* for coshf
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
value for which to return the hyperbolic cosine
int main(void)
{
float x, y;
errno = 0;
x = -1.0F;
y = coshf (x);
if (errno)
perror("Error");
printf("The hyperbolic cosine of %f is %f\n\n",
x, y);
errno = 0;
x = 0.0F;
y = coshf (x);
if (errno)
perror("Error");
printf("The hyperbolic cosine of %f is %f\n\n",
x, y);
errno = 0;
x = 720.0F;
y = coshf (x);
if (errno)
perror("Error");
printf("The hyperbolic cosine of %f is %f\n\n",
x, y);
}
Output:
The hyperbolic cosine of -1.000000 is 1.543081
The hyperbolic cosine of 0.000000 is 1.000000
Error: range error
The hyperbolic cosine of 720.000000 is inf
DS50001456J-page 166
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Standard C Libraries - Math Functions
exp
Description:
Calculates the exponential function of x (e raised to the power x where
x is a double precision floating-point value).
Include:
<math.h>
Prototype:
double exp (double x);
Argument:
x
Return Value:
Returns the exponential of x. On an overflow, exp returns inf and on
an underflow exp returns 0.
Remarks:
A range error occurs if the magnitude of x is too large.
Example:
#include <math.h> /* for exp
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
value for which to return the exponential
int main(void)
{
double x, y;
errno = 0;
x = 1.0;
y = exp (x);
if (errno)
perror("Error");
printf("The exponential of %f is %f\n\n", x, y);
errno = 0;
x = 1E3;
y = exp (x);
if (errno)
perror("Error");
printf("The exponential of %f is %f\n\n", x, y);
errno = 0;
x = -1E3;
y = exp (x);
if (errno)
perror("Error");
printf("The exponential of %f is %f\n\n", x, y);
}
Output:
The exponential of 1.000000 is 2.718282
Error: range error
The exponential of 1000.000000 is inf
Error: range error
The exponential of -1000.000000 is 0.000000
 2004-2014 Microchip Technology Inc.
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16-Bit Language Tools Libraries
expf
Description:
Calculates the exponential function of x (e raised to the power x where
x is a single precision floating-point value).
Include:
<math.h>
Prototype:
float expf (float x);
Argument:
x
Return Value:
Returns the exponential of x. On an overflow, expf returns inf and on
an underflow exp returns 0.
Remarks:
A range error occurs if the magnitude of x is too large.
Example:
#include <math.h> /* for expf
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
floating-point value for which to return the exponential
int main(void)
{
float x, y;
errno = 0;
x = 1.0F;
y = expf (x);
if (errno)
perror("Error");
printf("The exponential of %f is %f\n\n", x, y);
errno = 0;
x = 1.0E3F;
y = expf (x);
if (errno)
perror("Error");
printf("The exponential of %f is %f\n\n", x, y);
errno = 0;
x = -1.0E3F;
y = expf (x);
if (errno)
perror("Error");
printf("The exponential of %f is %f\n\n", x, y);
}
Output:
The exponential of 1.000000 is 2.718282
Error: range error
The exponential of 1000.000000 is inf
Error: range error
The exponential of -1000.000000 is 0.000000
DS50001456J-page 168
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Standard C Libraries - Math Functions
fabs
Description:
Calculates the absolute value of a double precision floating-point value.
Include:
<math.h>
Prototype:
double fabs(double x);
Argument:
x
Return Value:
Returns the absolute value of x. A negative number is returned as positive, a positive number is unchanged.
Remarks:
No domain or range error will occur.
Example:
#include <math.h> /* for fabs
*/
#include <stdio.h> /* for printf */
floating-point value for which to return the absolute value
int main(void)
{
double x, y;
x = 1.75;
y = fabs (x);
printf("The absolute value of
%f is
x = -1.5;
y = fabs (x);
printf("The absolute value of %f is
%f\n", x, y);
%f\n", x, y);
}
Output:
The absolute value of 1.750000 is
The absolute value of -1.500000 is
1.750000
1.500000
fabsf
Description:
Calculates the absolute value of a single precision floating-point value.
Include:
<math.h>
Prototype:
float fabsf(float x);
Argument:
x
Return Value:
Returns the absolute value of x. A negative number is returned as positive, a positive number is unchanged.
Remarks:
No domain or range error will occur.
Example:
#include <math.h> /* for fabsf */
#include <stdio.h> /* for printf */
floating-point value for which to return the absolute value
int main(void)
{
float x,y;
x = 1.75F;
y = fabsf (x);
printf("The absolute value of
%f is
x = -1.5F;
y = fabsf (x);
printf("The absolute value of %f is
%f\n", x, y);
%f\n", x, y);
}
Output:
The absolute value of 1.750000 is
The absolute value of -1.500000 is
 2004-2014 Microchip Technology Inc.
1.750000
1.500000
DS50001456J-page 169
16-Bit Language Tools Libraries
floor
Description:
Calculates the floor of a double precision floating-point value.
Include:
<math.h>
Prototype:
double floor (double x);
Argument:
x
Return Value:
Returns the largest integer value less than or equal to x.
Remarks:
No domain or range error will occur. See ceil.
Example:
#include <math.h> /* for floor */
#include <stdio.h> /* for printf */
floating-point value for which to return the floor
int main(void)
{
double x[8] = {2.0, 1.75, 1.5, 1.25, -2.0,
-1.75, -1.5, -1.25};
double y;
int i;
for (i=0; i<8; i++)
{
y = floor (x[i]);
printf("The ceiling for %f is %f\n", x[i], y);
}
}
Output:
The floor
The floor
The floor
The floor
The floor
The floor
The floor
The floor
for
for
for
for
for
for
for
for
2.000000 is 2.000000
1.750000 is 1.000000
1.500000 is 1.000000
1.250000 is 1.000000
-2.000000 is -2.000000
-1.750000 is -2.000000
-1.500000 is -2.000000
-1.250000 is -2.000000
floorf
DS50001456J-page 170
Description:
Calculates the floor of a single precision floating-point value.
Include:
<math.h>
Prototype:
float floorf(float x);
Argument:
x
Return Value:
Returns the largest integer value less than or equal to x.
Remarks:
No domain or range error will occur. See ceilf.
floating-point value
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Math Functions
floorf (Continued)
Example:
#include <math.h> /* for floorf */
#include <stdio.h> /* for printf */
int main(void)
{
float x[8] = {2.0F, 1.75F, 1.5F, 1.25F,
-2.0F, -1.75F, -1.5F, -1.25F};
float y;
int i;
for (i=0; i<8; i++)
{
y = floorf (x[i]);
printf("The floor for
}
%f is
%f\n", x[i], y);
}
Output:
The floor
The floor
The floor
The floor
The floor
The floor
The floor
The floor
for
for
for
for
for
for
for
for
2.000000 is
1.750000 is
1.500000 is
1.250000 is
-2.000000 is
-1.750000 is
-1.500000 is
-1.250000 is
2.000000
1.000000
1.000000
1.000000
-2.000000
-2.000000
-2.000000
-2.000000
fmod
Description:
Calculates the remainder of x/y as a double precision value.
Include:
<math.h>
Prototype:
double fmod(double x, double y);
Arguments:
x
a double precision floating-point value
y
a double precision floating-point value
Return Value:
Returns the remainder of x divided by y.
Remarks:
If y = 0, a domain error occurs. If y is non-zero, the result will have the
same sign as x and the magnitude of the result will be less than the
magnitude of y.
Example:
#include <math.h> /* for fmod
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
int main(void)
{
double x,y,z;
errno = 0;
x = 7.0;
y = 3.0;
z = fmod(x, y);
if (errno)
perror("Error");
printf("For fmod(%f, %f) the remainder is %f\n\n",
x, y, z);
 2004-2014 Microchip Technology Inc.
DS50001456J-page 171
16-Bit Language Tools Libraries
fmod (Continued)
errno = 0;
x = 7.0;
y = 7.0;
z = fmod(x, y);
if (errno)
perror("Error");
printf("For fmod(%f, %f) the remainder is %f\n\n",
x, y, z);
errno = 0;
x = -5.0;
y = 3.0;
z = fmod(x, y);
if (errno)
perror("Error");
printf("For fmod(%f, %f) the remainder is %f\n\n",
x, y, z);
errno = 0;
x = 5.0;
y = -3.0;
z = fmod(x, y);
if (errno)
perror("Error");
printf("For fmod(%f, %f) the remainder is %f\n\n",
x, y, z);
errno = 0;
x = -5.0;
y = -5.0;
z = fmod(x, y);
if (errno)
perror("Error");
printf("For fmod(%f, %f) the remainder is %f\n\n",
x, y, z);
errno = 0;
x = 7.0;
y = 0.0;
z = fmod(x, y);
if (errno)
perror("Error");
printf("For fmod(%f, %f) the remainder is %f\n\n",
x, y, z);
}
DS50001456J-page 172
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Math Functions
fmod (Continued)
Output:
For fmod(7.000000, 3.000000) the remainder is
1.000000
For fmod(7.000000, 7.000000) the remainder is
0.000000
For fmod(-5.000000, 3.000000) the remainder is
-2.000000
For fmod(5.000000, -3.000000) the remainder is
2.000000
For fmod(-5.000000, -5.000000) the remainder is
-0.000000
Error: domain error
For fmod(7.000000, 0.000000) the remainder is nan
fmodf
Description:
Calculates the remainder of x/y as a single precision value.
Include:
<math.h>
Prototype:
float fmodf(float x, float y);
Arguments:
x
a single precision floating-point value
y
a single precision floating-point value
Return Value:
Returns the remainder of x divided by y.
Remarks:
If y = 0, a domain error occurs. If y is non-zero, the result will have the
same sign as x and the magnitude of the result will be less than the
magnitude of y.
Example:
#include <math.h> /* for fmodf
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
int main(void)
{
float x,y,z;
errno = 0;
x = 7.0F;
y = 3.0F;
z = fmodf (x, y);
if (errno)
perror("Error");
printf("For fmodf (%f, %f) the remainder is"
" %f\n\n", x, y, z);
errno = 0;
x = -5.0F;
y = 3.0F;
z = fmodf (x, y);
if (errno)
perror("Error");
printf("For fmodf (%f, %f) the remainder is"
" %f\n\n", x, y, z);
 2004-2014 Microchip Technology Inc.
DS50001456J-page 173
16-Bit Language Tools Libraries
fmodf (Continued)
errno = 0;
x = 5.0F;
y = -3.0F;
z = fmodf (x, y);
if (errno)
perror("Error");
printf("For fmodf (%f, %f) the remainder is"
" %f\n\n", x, y, z);
errno = 0;
x = 5.0F;
y = -5.0F;
z = fmodf (x, y);
if (errno)
perror("Error");
printf("For fmodf (%f, %f) the remainder is"
" %f\n\n", x, y, z);
errno = 0;
x = 7.0F;
y = 0.0F;
z = fmodf (x, y);
if (errno)
perror("Error");
printf("For fmodf (%f, %f) the remainder is"
" %f\n\n", x, y, z);
errno = 0;
x = 7.0F;
y = 7.0F;
z = fmodf (x, y);
if (errno)
perror("Error");
printf("For fmodf (%f, %f) the remainder is"
" %f\n\n", x, y, z);
}
Output:
For fmodf (7.000000, 3.000000) the remainder is
1.000000
For fmodf (-5.000000, 3.000000) the remainder is
-2.000000
For fmodf (5.000000, -3.000000) the remainder is
2.000000
For fmodf (5.000000, -5.000000) the remainder is
0.000000
Error: domain error
For fmodf (7.000000, 0.000000) the remainder is nan
For fmodf (7.000000, 7.000000) the remainder is
0.000000
DS50001456J-page 174
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Math Functions
frexp
Description:
Gets the fraction and the exponent of a double precision floating-point
number.
Include:
<math.h>
Prototype:
double frexp (double x, int *exp);
Arguments:
x
floating-point value for which to return the fraction and exponent
exp pointer to a stored integer exponent
Return Value:
Returns the fraction, exp points to the exponent. If x is 0, the function
returns 0 for both the fraction and exponent.
Remarks:
The absolute value of the fraction is in the range of 1/2 (inclusive) to 1
(exclusive). No domain or range error will occur.
Example:
#include <math.h> /* for frexp */
#include <stdio.h> /* for printf */
int main(void)
{
double x,y;
int n;
x = 50.0;
y = frexp (x, &n);
printf("For frexp of %f\n the fraction is %f\n ",
x, y);
printf(" and the exponent is %d\n\n", n);
x = -2.5;
y = frexp (x, &n);
printf("For frexp of %f\n the fraction is %f\n ",
x, y);
printf(" and the exponent is %d\n\n", n);
x = 0.0;
y = frexp (x, &n);
printf("For frexp of %f\n the fraction is %f\n ",
x, y);
printf(" and the exponent is %d\n\n", n);
}
Output:
For frexp of 50.000000
the fraction is 0.781250
and the exponent is 6
For frexp of -2.500000
the fraction is -0.625000
and the exponent is 2
For frexp of 0.000000
the fraction is 0.000000
and the exponent is 0
 2004-2014 Microchip Technology Inc.
DS50001456J-page 175
16-Bit Language Tools Libraries
frexpf
Description:
Gets the fraction and the exponent of a single precision floating-point
number.
Include:
<math.h>
Prototype:
float frexpf (float x, int *exp);
Arguments:
x
floating-point value for which to return the fraction and exponent
exp pointer to a stored integer exponent
Return Value:
Returns the fraction, exp points to the exponent. If x is 0, the function
returns 0 for both the fraction and exponent.
Remarks:
The absolute value of the fraction is in the range of 1/2 (inclusive) to 1
(exclusive). No domain or range error will occur.
Example:
#include <math.h> /* for frexpf */
#include <stdio.h> /* for printf */
int main(void)
{
float x,y;
int n;
x = 0.15F;
y = frexpf (x, &n);
printf("For frexpf of %f\n the fraction is %f\n ",
x, y);
printf(" and the exponent is %d\n\n", n);
x = -2.5F;
y = frexpf (x, &n);
printf("For frexpf of %f\n the fraction is %f\n ",
x, y);
printf(" and the exponent is %d\n\n", n);
x = 0.0F;
y = frexpf (x, &n);
printf("For frexpf of %f\n the fraction is %f\n ",
x, y);
printf(" and the exponent is %d\n\n", n);
}
Output:
For frexpf of 0.150000
the fraction is 0.600000
and the exponent is -2
For frexpf of -2.500000
the fraction is -0.625000
and the exponent is 2
For frexpf of 0.000000
the fraction is 0.000000
and the exponent is 0
DS50001456J-page 176
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Math Functions
ldexp
Description:
Calculates the result of a double precision floating-point number
multiplied by an exponent of 2.
Include:
<math.h>
Prototype:
double ldexp(double x, int ex);
Arguments:
x
floating-point value
ex
integer exponent
Return Value:
Returns x * 2^ex. On an overflow, ldexp returns inf and on an
underflow, ldexp returns 0.
Remarks:
A range error will occur on overflow or underflow.
Example:
#include <math.h> /* for ldexp
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
int main(void)
{
double x,y;
int n;
errno = 0;
x = -0.625;
n = 2;
y = ldexp (x, n);
if (errno)
perror("Error");
printf("For a number = %f and an exponent = %d\n",
x, n);
printf(" ldexp(%f, %d) = %f\n\n",
x, n, y);
errno = 0;
x = 2.5;
n = 3;
y = ldexp (x, n);
if (errno)
perror("Error");
printf("For a number = %f and an exponent = %d\n",
x, n);
printf(" ldexp(%f, %d) = %f\n\n",
x, n, y);
errno = 0;
x = 15.0;
n = 10000;
y = ldexp (x, n);
if (errno)
perror("Error");
printf("For a number = %f and an exponent = %d\n",
x, n);
printf(" ldexp(%f, %d) = %f\n\n",
x, n, y);
}
 2004-2014 Microchip Technology Inc.
DS50001456J-page 177
16-Bit Language Tools Libraries
ldexp (Continued)
Output:
For a number = -0.625000 and an exponent = 2
ldexp(-0.625000, 2) = -2.500000
For a number = 2.500000 and an exponent = 3
ldexp(2.500000, 3) = 20.000000
Error: range error
For a number = 15.000000 and an exponent = 10000
ldexp(15.000000, 10000) = inf
ldexpf
Description:
Calculates the result of a single precision floating-point number
multiplied by an exponent of 2.
Include:
<math.h>
Prototype:
float ldexpf(float x, int ex);
Arguments:
x
floating-point value
ex
integer exponent
Return Value:
Returns x * 2^ex. On an overflow, ldexp returns inf and on an
underflow, ldexp returns 0.
Remarks:
A range error will occur on overflow or underflow.
Example:
#include <math.h> /* for ldexpf
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
int main(void)
{
float x,y;
int n;
errno = 0;
x = -0.625F;
n = 2;
y = ldexpf (x, n);
if (errno)
perror("Error");
printf("For a number = %f and an exponent = %d\n",
x, n);
printf(" ldexpf(%f, %d) = %f\n\n",
x, n, y);
errno = 0;
x = 2.5F;
n = 3;
y = ldexpf (x, n);
if (errno)
perror("Error");
printf("For a number = %f and an exponent = %d\n",
x, n);
printf(" ldexpf(%f, %d) = %f\n\n",
x, n, y);
DS50001456J-page 178
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Math Functions
ldexpf (Continued)
errno = 0;
x = 15.0F;
n = 10000;
y = ldexpf (x, n);
if (errno)
perror("Error");
printf("For a number = %f and an exponent = %d\n",
x, n);
printf(" ldexpf(%f, %d) = %f\n\n",
x, n, y);
}
Output:
For a number = -0.625000 and an exponent = 2
ldexpf(-0.625000, 2) = -2.500000
For a number = 2.500000 and an exponent = 3
ldexpf(2.500000, 3) = 20.000000
Error: range error
For a number = 15.000000 and an exponent = 10000
ldexpf(15.000000, 10000) = inf
 2004-2014 Microchip Technology Inc.
DS50001456J-page 179
16-Bit Language Tools Libraries
log
Description:
Calculates the natural logarithm of a double precision floating-point
value.
Include:
<math.h>
Prototype:
double log(double x);
Argument:
x
Return Value:
Returns the natural logarithm of x. -inf is returned if x is 0 and NaN is
returned if x is a negative number.
Remarks:
A domain error occurs if x  0.
Example:
#include <math.h> /* for log
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
any positive value for which to return the log
int main(void)
{
double x, y;
errno = 0;
x = 2.0;
y = log (x);
if (errno)
perror("Error");
printf("The natural logarithm of %f is %f\n\n",
x, y);
errno = 0;
x = 0.0;
y = log (x);
if (errno)
perror("Error");
printf("The natural logarithm of %f is %f\n\n",
x, y);
errno = 0;
x = -2.0;
y = log (x);
if (errno)
perror("Error");
printf("The natural logarithm of %f is %f\n\n",
x, y);
}
Output:
The natural logarithm of 2.000000 is 0.693147
The natural logarithm of 0.000000 is -inf
Error: domain error
The natural logarithm of -2.000000 is nan
DS50001456J-page 180
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Math Functions
log10
Description:
Calculates the base-10 logarithm of a double precision floating-point
value.
Include:
<math.h>
Prototype:
double log10(double x);
Argument:
x
Return Value:
Returns the base-10 logarithm of x. -inf is returned if x is 0 and NaN
is returned if x is a negative number.
Remarks:
A domain error occurs if x  0.
Example:
#include <math.h> /* for log10
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
any double precision floating-point positive number
int main(void)
{
double x, y;
errno = 0;
x = 2.0;
y = log10 (x);
if (errno)
perror("Error");
printf("The base-10 logarithm of %f is %f\n\n",
x, y);
errno = 0;
x = 0.0;
y = log10 (x);
if (errno)
perror("Error");
printf("The base-10 logarithm of %f is %f\n\n",
x, y);
errno = 0;
x = -2.0;
y = log10 (x);
if (errno)
perror("Error");
printf("The base-10 logarithm of %f is %f\n\n",
x, y);
}
Output:
The base-10 logarithm of 2.000000 is 0.301030
The base-10 logarithm of 0.000000 is -inf
Error: domain error
The base-10 logarithm of -2.000000 is nan
 2004-2014 Microchip Technology Inc.
DS50001456J-page 181
16-Bit Language Tools Libraries
log10f
Description:
Calculates the base-10 logarithm of a single precision floating-point
value.
Include:
<math.h>
Prototype:
float log10f(float x);
Argument:
x
Return Value:
Returns the base-10 logarithm of x. -inf is returned if x is 0 and NaN
is returned if x is a negative number.
Remarks:
A domain error occurs if x  0.
Example:
#include <math.h> /* for log10f
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
any single precision floating-point positive number
int main(void)
{
float x, y;
errno = 0;
x = 2.0F;
y = log10f(x);
if (errno)
perror("Error");
printf("The base-10 logarithm of %f is %f\n\n",
x, y);
errno = 0;
x = 0.0F;
y = log10f(x);
if (errno)
perror("Error");
printf("The base-10 logarithm of %f is %f\n\n",
x, y);
errno = 0;
x = -2.0F;
y = log10f(x);
if (errno)
perror("Error");
printf("The base-10 logarithm of %f is %f\n\n",
x, y);
}
Output:
The base-10 logarithm of 2.000000 is 0.301030
Error: domain error
The base-10 logarithm of 0.000000 is -inf
Error: domain error
The base-10 logarithm of -2.000000 is nan
DS50001456J-page 182
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Math Functions
logf
Description:
Calculates the natural logarithm of a single precision floating-point
value.
Include:
<math.h>
Prototype:
float logf(float x);
Argument:
x
Return Value:
Returns the natural logarithm of x. -inf is returned if x is 0 and NaN is
returned if x is a negative number.
Remarks:
A domain error occurs if x  0.
Example:
#include <math.h> /* for logf
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
any positive value for which to return the log
int main(void)
{
float x, y;
errno = 0;
x = 2.0F;
y = logf (x);
if (errno)
perror("Error");
printf("The natural logarithm of %f is %f\n\n",
x, y);
errno = 0;
x = 0.0F;
y = logf (x);
if (errno)
perror("Error");
printf("The natural logarithm of %f is %f\n\n",
x, y);
errno = 0;
x = -2.0F;
y = logf (x);
if (errno)
perror("Error");
printf("The natural logarithm of %f is %f\n\n",
x, y);
}
Output:
The natural logarithm of 2.000000 is 0.693147
The natural logarithm of 0.000000 is -inf
Error: domain error
The natural logarithm of -2.000000 is nan
 2004-2014 Microchip Technology Inc.
DS50001456J-page 183
16-Bit Language Tools Libraries
modf
Description:
Splits a double precision floating-point value into fractional and integer
parts.
Include:
<math.h>
Prototype:
double modf(double x, double *pint);
Arguments:
x
double precision floating-point value
pint
pointer to a stored the integer part
Return Value:
Returns the signed fractional part and pint points to the integer part.
Remarks:
The absolute value of the fractional part is in the range of 0 (inclusive)
to 1 (exclusive). No domain or range error will occur.
Example:
#include <math.h> /* for modf
*/
#include <stdio.h> /* for printf */
int main(void)
{
double x,y,n;
x = 0.707;
y = modf (x, &n);
printf("For %f the fraction is %f\n ", x, y);
printf(" and the integer is %0.f\n\n", n);
x = -15.2121;
y = modf (x, &n);
printf("For %f the fraction is %f\n ", x, y);
printf(" and the integer is %0.f\n\n", n);
}
Output:
For 0.707000 the fraction is 0.707000
and the integer is 0
For -15.212100 the fraction is -0.212100
and the integer is -15
DS50001456J-page 184
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Math Functions
modff
Description:
Splits a single precision floating-point value into fractional and integer
parts.
Include:
<math.h>
Prototype:
float modff(float x, float *pint);
Arguments:
x
single precision floating-point value
pint
pointer to stored integer part
Return Value:
Returns the signed fractional part and pint points to the integer part.
Remarks:
The absolute value of the fractional part is in the range of 0 (inclusive)
to 1 (exclusive). No domain or range error will occur.
Example:
#include <math.h> /* for modff */
#include <stdio.h> /* for printf */
int main(void)
{
float x,y,n;
x = 0.707F;
y = modff (x, &n);
printf("For %f the fraction is %f\n ", x, y);
printf(" and the integer is %0.f\n\n", n);
x = -15.2121F;
y = modff (x, &n);
printf("For %f the fraction is %f\n ", x, y);
printf(" and the integer is %0.f\n\n", n);
}
Output:
For 0.707000 the fraction is 0.707000
and the integer is 0
For -15.212100 the fraction is -0.212100
and the integer is -15
 2004-2014 Microchip Technology Inc.
DS50001456J-page 185
16-Bit Language Tools Libraries
pow
Description:
Calculates x raised to the power y.
Include:
<math.h>
Prototype:
double pow(double x, double y);
Arguments:
x
the base
y
the exponent
Return Value:
Returns x raised to the power y (x^y).
Remarks:
If y is 0, pow returns 1. If x is 0.0 and y is less than 0, pow returns inf
and a domain error occurs. If the result overflows or underflows, a
range error occurs.
Example:
#include <math.h> /* for pow
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
int main(void)
{
double x,y,z;
errno = 0;
x = -2.0;
y = 3.0;
z = pow (x, y);
if (errno)
perror("Error");
printf("%f raised to %f is %f\n\n ", x, y, z);
errno = 0;
x = 3.0;
y = -0.5;
z = pow (x, y);
if (errno)
perror("Error");
printf("%f raised to %f is %f\n\n ", x, y, z);
errno = 0;
x = 4.0;
y = 0.0;
z = pow (x, y);
if (errno)
perror("Error");
printf("%f raised to %f is %f\n\n ", x, y, z);
errno = 0;
x = 0.0;
y = -3.0;
z = pow (x, y);
if (errno)
perror("Error");
printf("%f raised to %f is %f\n\n ", x, y, z);
}
DS50001456J-page 186
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Math Functions
pow (Continued)
Output:
-2.000000 raised to 3.000000 is -8.000000
3.000000 raised to -0.500000 is 0.577350
4.000000 raised to 0.000000 is 1.000000
Error: domain error
0.000000 raised to -3.000000 is inf
powf
Description:
Calculates x raised to the power y.
Include:
<math.h>
Prototype:
float powf(float x, float y);
Arguments:
x
base
y
exponent
Return Value:
Returns x raised to the power y (x^y).
Remarks:
If y is 0, powf returns 1. If x is 0.0 and y is less than 0, powf returns
inf and a domain error occurs. If the result overflows or underflows, a
range error occurs.
Example:
#include <math.h> /* for powf
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
int main(void)
{
float x,y,z;
errno = 0;
x = -2.0F;
y = 3.0F;
z = powf (x, y);
if (errno)
perror("Error");
printf("%f raised to %f is %f\n\n ", x, y, z);
errno = 0;
x = 3.0F;
y = -0.5F;
z = powf (x, y);
if (errno)
perror("Error");
printf("%f raised to %f is %f\n\n ", x, y, z);
errno = 0;
x = 0.0F;
y = -3.0F;
z = powf (x, y);
if (errno)
perror("Error");
printf("%f raised to %f is %f\n\n ", x, y, z);
}
 2004-2014 Microchip Technology Inc.
DS50001456J-page 187
16-Bit Language Tools Libraries
powf (Continued)
Output:
-2.000000 raised to 3.000000 is -8.000000
3.000000 raised to -0.500000 is 0.577350
Error: domain error
0.000000 raised to -3.000000 is inf
sin
Description:
Calculates the trigonometric sine function of a double precision
floating-point value.
Include:
<math.h>
Prototype:
double sin (double x);
Argument:
x
Return Value:
Returns the sine of x in radians in the ranges of -1 to 1 inclusive.
Remarks:
A domain error will occur if x is a NaN or infinity.
Example:
#include <math.h> /* for sin
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
value for which to return the sine
int main(void)
{
double x, y;
errno = 0;
x = -1.0;
y = sin (x);
if (errno)
perror("Error");
printf("The sine of %f is %f\n\n", x, y);
errno = 0;
x = 0.0;
y = sin (x);
if (errno)
perror("Error");
printf("The sine of %f is %f\n\n", x, y);
}
Output:
The sine of -1.000000 is -0.841471
The sine of 0.000000 is 0.000000
DS50001456J-page 188
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Math Functions
sinf
Description:
Calculates the trigonometric sine function of a single precision
floating-point value.
Include:
<math.h>
Prototype:
float sinf (float x);
Argument:
x
Return Value:
Returns the sin of x in radians in the ranges of -1 to 1 inclusive.
Remarks:
A domain error will occur if x is a NaN or infinity.
Example:
#include <math.h> /* for sinf
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
value for which to return the sine
int main(void)
{
float x, y;
errno = 0;
x = -1.0F;
y = sinf (x);
if (errno)
perror("Error");
printf("The sine of %f is %f\n\n", x, y);
errno = 0;
x = 0.0F;
y = sinf (x);
if (errno)
perror("Error");
printf("The sine of %f is %f\n\n", x, y);
}
Output:
The sine of -1.000000 is -0.841471
The sine of 0.000000 is 0.000000
 2004-2014 Microchip Technology Inc.
DS50001456J-page 189
16-Bit Language Tools Libraries
sinh
Description:
Calculates the hyperbolic sine function of a double precision
floating-point value.
Include:
<math.h>
Prototype:
double sinh (double x);
Argument:
x
Return Value:
Returns the hyperbolic sine of x
Remarks:
A range error will occur if the magnitude of x is too large.
Example:
#include <math.h> /* for sinh
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
value for which to return the hyperbolic sine
int main(void)
{
double x, y;
errno = 0;
x = -1.5;
y = sinh (x);
if (errno)
perror("Error");
printf("The hyperbolic sine of %f is %f\n\n",
x, y);
errno = 0;
x = 0.0;
y = sinh (x);
if (errno)
perror("Error");
printf("The hyperbolic sine of %f is %f\n\n",
x, y);
errno = 0;
x = 720.0;
y = sinh (x);
if (errno)
perror("Error");
printf("The hyperbolic sine of %f is %f\n\n",
x, y);
}
Output:
The hyperbolic sine of -1.500000 is -2.129279
The hyperbolic sine of 0.000000 is 0.000000
Error: range error
The hyperbolic sine of 720.000000 is inf
DS50001456J-page 190
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Math Functions
sinhf
Description:
Calculates the hyperbolic sine function of a single precision
floating-point value.
Include:
<math.h>
Prototype:
float sinhf (float x);
Argument:
x
Return Value:
Returns the hyperbolic sine of x .
Remarks:
A range error will occur if the magnitude of x is too large.
Example:
#include <math.h> /* for sinhf
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
value for which to return the hyperbolic sine
int main(void)
{
float x, y;
errno = 0;
x = -1.0F;
y = sinhf (x);
if (errno)
perror("Error");
printf("The hyperbolic sine of %f is %f\n\n",
x, y);
errno = 0;
x = 0.0F;
y = sinhf (x);
if (errno)
perror("Error");
printf("The hyperbolic sine of %f is %f\n\n",
x, y);
}
Output:
The hyperbolic sine of -1.000000 is -1.175201
The hyperbolic sine of 0.000000 is 0.000000
 2004-2014 Microchip Technology Inc.
DS50001456J-page 191
16-Bit Language Tools Libraries
sqrt
Description:
Calculates the square root of a double precision floating-point value.
Include:
<math.h>
Prototype:
double sqrt(double x);
Argument:
x
Return Value:
Returns the non-negative square root of x.
Remarks:
If x is negative, a domain error occurs.
Example:
#include <math.h> /* for sqrt
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
a non-negative floating-point value
int main(void)
{
double x, y;
errno = 0;
x = 0.0;
y = sqrt (x);
if (errno)
perror("Error");
printf("The square root of %f is %f\n\n", x, y);
errno = 0;
x = 9.5;
y = sqrt (x);
if (errno)
perror("Error");
printf("The square root of %f is %f\n\n", x, y);
errno = 0;
x = -25.0;
y = sqrt (x);
if (errno)
perror("Error");
printf("The square root of %f is %f\n\n", x, y);
}
Output:
The square root of 0.000000 is 0.000000
The square root of 9.500000 is 3.082207
Error: domain error
The square root of -25.000000 is nan
DS50001456J-page 192
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Math Functions
sqrtf
Description:
Calculates the square root of a single precision floating-point value.
Include:
<math.h>
Prototype:
float sqrtf(float x);
Argument:
x
Return Value:
Returns the non-negative square root of x.
Remarks:
If x is negative, a domain error occurs.
Example:
#include <math.h> /* for sqrtf
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
non-negative floating-point value
int main(void)
{
double x;
errno = 0;
x = sqrtf (0.0F);
if (errno)
perror("Error");
printf("The square root of 0.0F is %f\n\n", x);
errno = 0;
x = sqrtf (9.5F);
if (errno)
perror("Error");
printf("The square root of 9.5F is %f\n\n", x);
errno = 0;
x = sqrtf (-25.0F);
if (errno)
perror("Error");
printf("The square root of -25F is %f\n", x);
}
Output:
The square root of 0.0F is 0.000000
The square root of 9.5F is 3.082207
Error: domain error
The square root of -25F is nan
 2004-2014 Microchip Technology Inc.
DS50001456J-page 193
16-Bit Language Tools Libraries
tan
Description:
Calculates the trigonometric tangent function of a double precision
floating-point value.
Include:
<math.h>
Prototype:
double tan (double x);
Argument:
x
Return Value:
Returns the tangent of x in radians.
Remarks:
A domain error will occur if x is a NaN or infinity.
Example:
#include <math.h> /* for tan
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
value for which to return the tangent
int main(void)
{
double x, y;
errno = 0;
x = -1.0;
y = tan (x);
if (errno)
perror("Error");
printf("The tangent of %f is %f\n\n", x, y);
errno = 0;
x = 0.0;
y = tan (x);
if (errno)
perror("Error");
printf("The tangent of %f is %f\n\n", x, y);
}
Output:
The tangent of -1.000000 is -1.557408
The tangent of 0.000000 is 0.000000
tanf
Description:
Calculates the trigonometric tangent function of a single precision
floating-point value.
Include:
<math.h>
Prototype:
float tanf (float x);
Argument:
x
Return Value:
Returns the tangent of x.
Remarks:
A domain error will occur if x is a NaN or infinity.
Example:
#include <math.h> /* for tanf
*/
#include <stdio.h> /* for printf, perror */
#include <errno.h> /* for errno
*/
value for which to return the tangent
int main(void)
{
float x, y;
DS50001456J-page 194
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Math Functions
tanf (Continued)
errno = 0;
x = -1.0F;
y = tanf (x);
if (errno)
perror("Error");
printf("The tangent of %f is %f\n\n", x, y);
errno = 0;
x = 0.0F;
y = tanf (x);
if (errno)
perror("Error");
printf("The tangent of %f is %f\n", x, y);
}
Output:
The tangent of -1.000000 is -1.557408
The tangent of 0.000000 is 0.000000
tanh
Description:
Calculates the hyperbolic tangent function of a double precision
floating-point value.
Include:
<math.h>
Prototype:
double tanh (double x);
Argument:
x
Return Value:
Returns the hyperbolic tangent of x in the ranges of -1 to 1 inclusive.
Remarks:
No domain or range error will occur.
Example:
#include <math.h> /* for tanh
*/
#include <stdio.h> /* for printf */
value for which to return the hyperbolic tangent
int main(void)
{
double x, y;
x = -1.0;
y = tanh (x);
printf("The hyperbolic tangent of %f is %f\n\n",
x, y);
x = 2.0;
y = tanh (x);
printf("The hyperbolic tangent of %f is %f\n\n",
x, y);
}
Output:
The hyperbolic tangent of -1.000000 is -0.761594
The hyperbolic tangent of 2.000000 is 0.964028
 2004-2014 Microchip Technology Inc.
DS50001456J-page 195
16-Bit Language Tools Libraries
tanhf
Description:
Calculates the hyperbolic tangent function of a single precision
floating-point value.
Include:
<math.h>
Prototype:
float tanhf (float x);
Argument:
x
Return Value:
Returns the hyperbolic tangent of x in the ranges of -1 to 1 inclusive.
Remarks:
No domain or range error will occur.
Example:
#include <math.h> /* for tanhf */
#include <stdio.h> /* for printf */
value for which to return the hyperbolic tangent
int main(void)
{
float x, y;
x = -1.0F;
y = tanhf (x);
printf("The hyperbolic tangent of %f is %f\n\n",
x, y);
x = 0.0F;
y = tanhf (x);
printf("The hyperbolic tangent of %f is %f\n\n",
x, y);
}
Output:
The hyperbolic tangent of -1.000000 is -0.761594
The hyperbolic tangent of 0.000000 is 0.000000
DS50001456J-page 196
 2004-2014 Microchip Technology Inc.
16-BIT LANGUAGE TOOLS
LIBRARIES
Chapter 4. Standard C Libraries - Support Functions
4.1
INTRODUCTION
This chapter describes support functions that either must be customized for correct
operation of the Standard C Library in your target environment or are already customized for a Microchip target environment. The default behavior section describes what
the function does as it is distributed. The description and remarks describe what it
typically should do.
The corresponding object modules are distributed in the libpic30-omf.a archive, and
the source code (for the compiler) is available in the src\pic30 folder.
4.1.1
Assembly Code Applications
A free version of this library and its associated header file is available from the
Microchip web site. Source code is included.
4.1.2
C Code Applications
The MPLAB XC16 C Compiler install directory (Section 1.1.1 “Compiler Installation
Locations”) contains the following subdirectories with library-related files:
• lib – standard C library files
• src\pic30 – source code for library functions, batch file to rebuild the library
• support\h – header files for libraries
In addition, there is a file, ResourceGraphs.pdf, which contains diagrams of resources
used by each function, located in lib.
4.1.3
Chapter Organization
This chapter is organized as follows:
•
•
•
•
•
•
•
Using the Support Functions
Standard C Library Helper Functions
Standard C Library Functions That Require Modification
Functions/Constants to Support A Simulated UART
Functions for Erasing and Writing EEDATA Memory
Functions for Erasing and Writing Flash Memory
Functions for Specialized Copying and Initialization
 2004-2014 Microchip Technology Inc.
DS50001456J-page 197
16-Bit Language Tools Libraries
4.2
USING THE SUPPORT FUNCTIONS
Building an application which utilizes the support functions requires two types of files:
header files and library files.
• Rebuilding the libpic30-omf.a Library
4.2.1
Header Files
All standard C library entities are declared or defined in one or more standard headers
(See list in Section 4.1.3 “Chapter Organization”.) To make use of a library entity in
a program, write an include directive that names the relevant standard header.
The contents of a standard header is included by naming it in an include directive, as in:
#include <libpic30.h> /* include dsPIC30F facilities */
The standard headers can be included in any order. Do not include a standard header
within a declaration. Do not define macros that have the same names as keywords
before including a standard header.
A standard header never includes another standard header.
4.2.2
Library Files
The archived library files contain all the individual object files for each library function.
When linking an application, the library file must be provided as an input to the linker
(using the --library or -l linker option) such that the functions used by the
application may be linked into the application.
A typical C application will require three library files: libc-omf.a, libm-omf.a and
libpic30-omf.a. (See Section 1.2 “OMF-Specific Libraries/Start-up Modules” for
more on OMF-specific libraries.) These libraries will be included automatically if linking
is performed using the compiler.
Note:
4.2.3
Some standard library functions require a heap. These include the standard
I/O functions that open files and the memory allocation functions. See the
“MPLAB® XC16 Assembler, Linker and Utilities User’s Guide” (DS50002106)
and “MPLAB® XC16 C Compiler User’s Guide” (DS50002071) for more
information on the heap.
Rebuilding the libpic30-omf.a Library
By default, the helper functions listed in this chapter were written to work with the sim30
simulator. The header file simio.h defines the interface between the library and the
simulator. It is provided so you can rebuild the libraries and continue to use the simulator. However, your application should not use this interface since the simulator will not
be available to an embedded application.
The helper functions must be modified and rebuilt for your target application. The libpic30-omf.a library can be rebuilt with the batch file named makelib.bat which has
been provided with the sources in src\pic30. Execute the batch file from a command
window. Be sure you are in the src\pic30 directory. Then, copy the newly compiled
file (libpic30-omf.a) into the lib directory.
DS50001456J-page 198
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Support Functions
4.3
STANDARD C LIBRARY HELPER FUNCTIONS
These functions are called by other functions in the standard C library and must be
modified for the target application. The corresponding object modules are distributed in
the libpic30-omf.a archive, and the source code (for the compiler) is available in the
src\pic30 folder.
_dump_heap_info
Description:
Displays the current use/free state of the heap.
Include:
None
Prototype:
void _dump_heap_info();
Argument:
None
Remarks:
This helper function can be used to profile memory allocation in the
heap. It is useful for memory allocation functions.
Default Behavior:
This function prints information about the heap to stderr. Information
includes the memory region where heap is located, the different sections of the heap, whether a section is currently busy or free, and a
summary of how much heap is free.
For example, below, a heap of 1000 has been allocated. The heap
begins and ends at d0c and 10f4, respectively. The malloc function
has been executed 3 different times, resulting in 3 different sections of
BUSY memory and 1 FREE memory section of heap that has not been
used. If the free function were to be used on any of these 3 allocated
sections, the status would turn from BUSY to FREE as well.
*** Unused Heap status:
***
start: 0x00000d0c
end: 0x000010f4
***
0d0c
8 BUSY
***
0d14
16 BUSY
***
0d24
20 BUSY
***
0d38
956 FREE
***
44 used, 956 free, 010f0 end
File:
_dump_heap_info.c
_exit
Description:
Terminate program execution.
Include:
None
Prototype:
void _exit (int status);
Argument:
status
Remarks:
This is a helper function called by the exit() Standard C Library
function.
Default Behavior:
As distributed, this function flushes stdout and terminates. The parameter status is the same as that passed to the exit() standard C library
function.
File:
_exit.c
 2004-2014 Microchip Technology Inc.
exit status
DS50001456J-page 199
16-Bit Language Tools Libraries
brk
Description:
Set the end of the process’s data space.
Include:
None
Prototype:
int brk(void *endds);
Argument:
endds
Return Value:
Returns ‘0’ if successful; otherwise, returns ‘-1’.
Remarks:
brk() is used to dynamically change the amount of space allocated for
the calling process’s data segment. The change is made by resetting
the process’s break value and allocating the appropriate amount of
space. The break value is the address of the first location beyond the
end of the data segment. The amount of allocated space increases as
the break value increases.
Newly allocated space is uninitialized.
This helper function is used by the Standard C Library function
malloc().
Default Behavior:
If the argument endds is zero, the function sets the global variable
__curbrk to the address of the start of the heap and returns zero.
If the argument endds is non-zero and has a value less than the
address of the end of the heap, the function sets the global variable
__curbrk to the value of endds and returns zero.
Otherwise, the global variable __curbrk is unchanged and the
function returns -1.
The argument endds must be within the heap range (see data space
memory map below).
pointer to the end of the data segment
PSV
Stack
Heap
Variables
SFR
Notice that, since the stack is located immediately above the heap,
using brk() or sbrk() has little effect on the size of the dynamic
memory pool. The brk() and sbrk() functions are primarily intended
for use in run-time environments where the stack grows downward and
the heap grows upward.
The linker allocates a block of memory for the heap if the
-Wl,--heap=n option is specified, where n is the desired heap size in
characters. The starting and ending addresses of the heap are reported
in variables: _heap and _eheap, respectively.
For the 16-bit compiler, using the linker’s heap size option is the standard way of controlling heap size, rather than relying on brk() and
sbrk().
File:
DS50001456J-page 200
brk.c
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Support Functions
close
Description:
Close a file.
Include:
None
Prototype:
int close(int handle);
Argument:
handle
Return Value:
Returns ‘0’ if the file is successfully closed. A return value of ‘-1’
indicates an error.
Remarks:
This helper function is called by the fclose() Standard C Library
function.
Default Behavior:
As distributed, this function passes the file handle to the simulator,
which issues a close in the host file system.
File:
close.c
handle referring to an opened file
lseek
Description:
Move a file pointer to a specified location.
Include:
None
Prototype:
long lseek(int handle, long offset, int origin);
Argument:
handle
offset
origin
Return Value:
Returns the offset, in characters, of the new position from the beginning
of the file. A return value of ‘-1L’ indicates an error.
Remarks:
This helper function is called by the Standard C Library functions
fgetpos(), ftell(), fseek(), fsetpos and rewind().
Default Behavior:
As distributed, the parameters are passed to the host file system
through the simulator. The return value is the value returned by the host
file system.
File:
lseek.c
refers to an opened file
the number of characters from the origin
the position from which to start the seek. origin may
be one of the following values (as defined in stdio.h):
SEEK_SET – Beginning of file.
SEEK_CUR – Current position of file pointer.
SEEK_END – End-of-file.
open
Description:
Open a file.
Include:
None
Prototype:
int open(const char *name, int access, int mode);
Argument:
name
access
mode
Return Value:
If successful, the function returns a file handle: a small positive integer.
This handle is then used on subsequent low-level file I/O operations. A
return value of ‘-1’ indicates an error.
 2004-2014 Microchip Technology Inc.
name of the file to be opened
access method to open file
type of access permitted
DS50001456J-page 201
16-Bit Language Tools Libraries
open (Continued)
Remarks:
The access flag is a union of one of the following access methods and
zero or more access qualifiers:
0 – Open a file for reading.
1 – Open a file for writing.
2 – Open a file for both reading and writing.
The following access qualifiers must be supported:
0x0008 – Move file pointer to end-of-file before every write operation.
0x0100 – Create and open a new file for writing.
0x0200 – Open the file and truncate it to zero length.
0x4000 – Open the file in text (translated) mode.
0x8000 – Open the file in binary (untranslated) mode.
The mode parameter may be one of the following:
0x0100 – Reading only permitted.
0x0080 – Writing permitted (implies reading permitted).
This helper function is called by the Standard C Library functions
fopen() and freopen().
Default Behavior:
As distributed, the parameters are passed to the host file system
through the simulator. The return value is the value returned by the host
file system. If the host system returns a value of ‘-1’, the global variable
errno is set to the value of the symbolic constant, EFOPEN, defined in
<errno.h>.
File:
open.c
read
Description:
Read data from a file.
Include:
None
Prototype:
int read(int handle, void *buffer,
unsigned int len);
Argument:
handle
buffer
len
Return Value:
Returns the number of characters read, which may be less than len if
there are fewer than len characters left in the file or if the file was
opened in text mode, in which case, each carriage return-linefeed
(CR-LF) pair is replaced with a single linefeed character. Only the
single linefeed character is counted in the return value. The replacement does not affect the file pointer. If the function tries to read at
end-of-file, it returns ‘0’. If the handle is invalid, or the file is not open for
reading or the file is locked, the function returns ‘-1’.
Remarks:
This helper function is called by the Standard C Library functions
fgetc(), fgets(), fread() and gets().
Default Behavior:
As distributed, the parameters are passed to the host file system
through the simulator. The return value is the value returned by the host
file system.
File:
read.c
handle referring to an opened file
points to the storage location for read data
the maximum number of characters to read
sbrk
DS50001456J-page 202
Description:
Extend the process’ data space by a given increment.
Include:
None
Prototype:
void * sbrk(int incr);
Argument:
incr
number of characters to increment/decrement
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Support Functions
sbrk (Continued)
Return Value:
Return the start of the new space allocated or ‘-1’ for errors.
Remarks:
sbrk() adds incr characters to the break value and changes the
allocated space accordingly. incr can be negative, in which case the
amount of allocated space is decreased.
sbrk() is used to dynamically change the amount of space allocated
for the calling process’s data segment. The change is made by resetting the process’s break value and allocating the appropriate amount of
space. The break value is the address of the first location beyond the
end of the data segment. The amount of allocated space increases as
the break value increases.
This is a helper function called by the Standard C Library function
malloc().
Default Behavior:
If the global variable __curbrk is zero, the function calls brk() to initialize the break value. If brk() returns -1, so does this function.
If the incr is zero, the current value of the global variable __curbrk
is returned.
If the incr is non-zero, the function checks that the address
(__curbrk + incr) is less than the end address of the heap. If it is
less, the global variable __curbrk is updated to that value and the
function returns the unsigned value of __curbrk.
Otherwise, the function returns -1.
See the description of brk().
File:
sbrk.c
write
Description:
Write data to a file.
Include:
None
Prototype:
int __attribute__((__section__(".libc.write")))
write(int handle, void *buffer, unsigned int count);
Argument:
handle
buffer
count
Return Value:
If successful, write returns the number of characters actually written. A
return value of ‘-1’ indicates an error.
Remarks:
If the actual space remaining on the disk is less than the size of the buffer, the function trying to write to the disk write fails and does not flush
any of the buffer’s contents to the disk. If the file is opened in text mode,
each linefeed character is replaced with a carriage return – linefeed
pair in the output. The replacement does not affect the return value.
This is a helper function called by the Standard C Library function
fflush().
Default Behavior:
As distributed, the parameters are passed to the host file system
through the simulator. The return value is the value returned by the host
file system.
File:
write.c
 2004-2014 Microchip Technology Inc.
refers to an opened file
points to the storage location of data to be written
the number of characters to write.
DS50001456J-page 203
16-Bit Language Tools Libraries
4.4
STANDARD C LIBRARY FUNCTIONS THAT REQUIRE MODIFICATION
Although these functions are part of the Standard C Library, the object modules are
distributed in the libpic30-omf.a archive and the source code (for the compiler) is
available in the src\pic30 folder. These modules are not distributed as part of
libc-omf.a.
getenv
Description:
Get a value for an environment variable.
Include:
<stdlib.h>
Prototype:
char *getenv(const char *s);
Argument:
s
Return Value:
Returns a pointer to the value of the environment variable if successful;
otherwise, returns a null pointer.
Default Behavior:
As distributed, this function returns a null pointer. There is no support
for environment variables.
File:
getenv.c
name of environment variable
remove
Description:
Remove a file.
Include:
<stdio.h>
Prototype:
int remove(const char *filename);
Argument:
filename
Return Value:
Returns ‘0’ if successful, ‘-1’ if unsuccessful.
Default Behavior:
As distributed, the parameters are passed to the host file system
through the simulator. The return value is the value returned by the host
file system.
File:
remove.c
file to be removed
rename
Description:
Rename a file or directory.
Include:
<stdio.h>
Prototype:
int rename(const char *oldname, const char
*newname);
Argument:
oldname
newname
Return Value:
Returns ‘0’ if it is successful. On an error, the function returns a
non-zero value.
Default Behavior:
As distributed, the parameters are passed to the host file system
through the simulator. The return value is the value returned by the host
file system.
File:
rename.c
pointer to the old name
pointer to the new name
system
DS50001456J-page 204
Description:
Execute a command.
Include:
<stdlib.h>
Prototype:
int system(const char *s);
Argument:
s
command to be executed
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Support Functions
system (Continued)
Default Behavior:
As distributed, this function acts as a stub or placeholder for your
function. If s is not NULL, an error message is written to stdout and
the program will reset; otherwise, a value of -1 is returned.
File:
system.c
time
4.5
Description:
Get the system time.
Include:
<time.h>
Prototype:
time_t time(time_t *timer);
Argument:
timer
Return Value:
Returns the elapse time in seconds. There is no error return.
Default Behavior:
As distributed, if Timer2 is not enabled, it is enabled in 32-bit mode. The
return value is the current value of the 32-bit Timer2 register. Except in
very rare cases, this return value is not the elapsed time in seconds.
File:
time.c
points to a storage location for time
FUNCTIONS/CONSTANTS TO SUPPORT A SIMULATED UART
These functions and constants support UART functionality in the MPLAB SIM simulator.
__attach_input_file
Description:
Attach a hosted file to the standard input stream.
Include:
<libpic30.h>
Prototype:
int __attach_input_file(const char *p);
Argument:
p
Remarks:
This function differs from the MPLAB IDE or MPLAB X IDE mechanism
of providing an input file because it provides “on-demand” access to the
file. That is, data will only be read from the file upon request and the
asynchronous nature of the UART is not simulated. This function may
be called more than once; any opened file will be closed. It is only
appropriate to call this function in a simulated environment.
Default Behavior:
Allows the programmer to attach a hosted file to the standard input
stream, stdin.
The function will return 0 to indicate failure. If the file cannot be opened
for whatever reason, standard in will remain connected (or be
re-connected) to the simulated UART.
File:
attach.c
pointer to file
__close_input_file
Description:
Close a previously attached file.
Include:
<libpic30.h>
Prototype:
void __close_input_file(void);
Argument:
None
Remarks:
None.
Default Behavior:
This function will close a previously attached file and re-attach stdin
to the simulated UART. This should occur before a Reset to ensure that
the file can be re-opened.
File:
close.c
 2004-2014 Microchip Technology Inc.
DS50001456J-page 205
16-Bit Language Tools Libraries
__delay32
Description:
Produce a delay of a specified number of clock cycles.
Include:
<libpic30.h>
Prototype:
void __delay32(unsigned long cycles);
Argument:
cycles
Remarks:
None.
Default Behavior:
This function will effect a delay of the requested number of cycles. The
minimum supported delay is 12 cycles (an argument of less than or
equal to 12 will result in 12 cycles). The delay includes the call and
return statements, but not any cycles required to set up the argument
(typically this would be two for a literal value).
File:
delay32.s
number of cycles to delay
__delay_ms
Description:
Produce a delay of a specified number of milliseconds (ms).
Include:
<libpic30.h>
Prototype:
void __delay_ms(unsigned int time);
Argument:
time
Remarks:
This function is implemented as a macro.
Default Behavior:
This function relies on a user-supplied definition of FCY to represent the
instruction clock frequency. FCY must be defined before header file libpic30.h is included. The specified delay is converted to the equivalent
number of instruction cycles and passed to __delay32(). If FCY is not
defined, then __delay_ms() is declared external, causing the link to fail
unless the user provides a function with that name.
File:
delay32.s
number of ms to delay
__delay_us
Description:
Produce a delay of a specified number of microseconds (us).
Include:
<libpic30.h>
Prototype:
void __delay_us(unsigned int time);
Argument:
time
Remarks:
This function is implemented as a macro. The minimum delay is
equivalent to 12 instruction cycles.
Default Behavior:
This function relies on a user-supplied definition of FCY to represent the
instruction clock frequency. FCY must be defined before header file,
libpic30.h, is included. The specified delay is converted to the
equivalent number of instruction cycles and passed to __delay32().
If FCY is not defined, then __delay_us() is declared external, causing the link to fail unless the user provides a function with that name.
File:
delay32.s
number of us to delay
__C30_UART
DS50001456J-page 206
Description:
Constant that defines the default UART.
Include:
N/A
Prototype:
int __C30_UART;
Argument:
N/A
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Support Functions
__C30_UART (Continued)
Return Value:
N/A
Remarks:
Defines the default UART that read() and write() will use for
stdin (unless a file has been attached) and stdout.
Default Behavior:
By default, or with a value of 1, UART 1 will be used. Otherwise,
UART 2 will be used. read() and write() are the eventual
destinations of the C standard I/O functions.
File:
N/A
Examples of Use
EXAMPLE 4-1:
UART1 I/O
#include <libpic30.h>
/* a new header file for
these defintions */
#include <stdio.h>
void main() {
if (__attach_input_file("foo.txt")) {
while (!feof(stdin)) {
putchar(getchar());
}
__close_input_file();
}
}
EXAMPLE 4-2:
USING UART2
/* This program flashes a light and transmits a lot of messages at
9600 8n1 through uart 2 using the default stdio provided
by the 16-bit compiler. This is for a dsPIC33F DSC
on an Explorer 16(tm) board (and isn't very pretty) */
#include <libpic30.h>
/* a new header file for these
defintions */
#include <stdio.h>
#ifndef __dsPIC33F__
#error this is a 33F demo for the explorer 16(tm) board
#endif
#inlcude <p33Fxxxx.h>
_FOSCSEL(FNOSC_PRI );
_FOSC(FCKSM_CSDCMD & OSCIOFNC_OFF & POSCMD_XT);
_FWDT(FWDTEN_OFF);
main() {
ODCA = 0;
TRISAbits.TRISA6 = 0;
__C30_UART=2;
U2BRG = 38;
U2MODEbits.UARTEN = 1;
while (1) {
__builtin_btg(&LATA,6);
printf("Hello world %d\n",U2BRG);
}
}
 2004-2014 Microchip Technology Inc.
DS50001456J-page 207
16-Bit Language Tools Libraries
EXAMPLE 4-3:
MILLISECOND DELAY
#define FCY 1000000UL
#include <libpic30.h>
int main()
{
/* at 1MHz, these are equivalent */
__delay_ms(1);
__delay32(1000);
}
EXAMPLE 4-4:
MICROSECOND DELAY
#define FCY 1000000UL
#include <libpic30.h>
int main()
{
/* at 1MHz, these are equivalent */
__delay_us(1000);
__delay32(1000);
}
4.6
FUNCTIONS FOR ERASING AND WRITING EEDATA MEMORY
These functions support the erasing and writing of EEDATA memory for devices that
have this type of memory.
_erase_eedata
Description:
Erase EEDATA memory on dsPIC30F and PIC24FXXKA devices.
Include:
<libpic30.h>
Prototype:
void _erase_eedata(_prog_addressT dst, int len);
Argument:
dst
len
Return Value:
None.
Remarks:
None.
Default Behavior:
Erase EEDATA memory as specified by parameters.
File:
eedata_helper.c
destination memory address
dsPIC30F: length may be _EE_WORD or _EE_ROW
(bytes)
PIC24FxxKA: length may be _EE_WORD, _EE_4WORDS
or _EE_8WORDS (bytes)
_erase_eedata_all
DS50001456J-page 208
Description:
Erase the entire range of EEDATA memory on dsPIC30F and
PIC24FXXKA devices.
Include:
<libpic30.h>
Prototype:
void _erase_eedata_all(void);
Argument:
None
Return Value:
None.
Remarks:
None.
Default Behavior:
Erase all EEDATA memory for the selected device.
File:
eedata_helper.c
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Support Functions
_wait_eedata
Description:
Wait for an erase or write operation to complete on dsPIC30F and
PIC24FXXKA devices.
Include:
<libpic30.h>
Prototype:
void _wait_eedata(void);
Argument:
None
Return Value:
None.
Remarks:
None.
Default Behavior:
Wait for an erase or write operation to complete.
File:
eedata_helper.c
_write_eedata_word
Description:
Write 16 bits of EEDATA memory on dsPIC30F and PIC24FXXKA
devices.
Include:
<libpic30.h>
Prototype:
void _write_eedata_word(_prog_addressT dst,
int dat);
Argument:
dst
dat
Return Value:
None.
Remarks:
None.
Default Behavior:
Write one word of EEDATA memory for dsPIC30F devices.
File:
eedata_helper.c
destination memory address
integer data to be written
_write_eedata_row
Description:
Write _EE_ROW bytes of EEDATA memory on dsPIC30F devices.
Include:
<libpic30.h>
Prototype:
void _write_eedata_row(_prog_addressT dst,
int *src);
Argument:
dst
*src
Return Value:
None.
Remarks:
None.
Default Behavior:
Write specified bytes of EEDATA memory.
File:
eedata_helper.c
 2004-2014 Microchip Technology Inc.
destination memory address
points to the storage location of data to be written
DS50001456J-page 209
16-Bit Language Tools Libraries
Example of Use – dsPIC30F DSCs
#include "libpic30.h"
#include "p30fxxxx.h"
char __attribute__((space(eedata), aligned(_EE_ROW))) dat[_EE_ROW];
int main()
{
char i,source[_EE_ROW];
_prog_addressT p;
for (i = 0; i < _EE_ROW; )
source[i] = i++;
/* initialize some data */
_init_prog_address(p, dat);
/* get address in program space */
_erase_eedata(p, _EE_ROW);
/* erase a row */
_wait_eedata();
/* wait for operation to complete */
_write_eedata_row(p, source);
/* write a row */
}
Example of Use – PIC24FXXKA MCUs
#include "libpic30.h"
#include "p24Fxxxx.h"
int
/* should use <> here */
__attribute__((space(eedata), aligned(_EE_4WORDS)))
dat[_EE_4WORDS/2];
int main()
{
_prog_addressT p;
_init_prog_address(p, dat);
_erase_eedata(p, _EE_4WORDS);
_wait_eedata();
_write_eedata_word(p, 0x1234);
_wait_eedata();
p += 2;
_write_eedata_word(p, 0x5678);
_wait_eedata();
/* get address in program
space */
/* erase the dat[] array */
/* wait to complete */
/* write a word to dat[0] */
/* write a word to dat[1] */
}
DS50001456J-page 210
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Support Functions
4.7
FUNCTIONS FOR ERASING AND WRITING FLASH MEMORY
These functions support the erasing and writing of Flash memory for devices that have
this type of memory.
_erase_flash
Description:
Erase a page of Flash memory. The length of a page is _FLASH_PAGE
words (1 word = 3 bytes = 2 PC address units).
Include:
<libpic30.h>
Prototype:
void _erase_flash(_prog_addressT dst);
Argument:
dst
Return Value:
None.
Remarks:
None.
Default Behavior:
Erase a page of Flash memory.
File:
flash_helper.s
destination memory address
_erase_flash (PIC24FXXKA Only)
Description:
Erase rows of Flash memory, either one, two or four rows.
Include:
<libpic30.h>
Prototype:
void _erase_flash(_prog_addressT dst, int len);
Argument:
dst
len
Return Value:
None.
Remarks:
None.
Default Behavior:
Erase rows of Flash memory.
File:
flash_helper2.s
destination memory address
length may be _FLASH_ROW, _FLASH_2ROWs or
_FLASH_4ROWS (bytes)
_write_flash16
Description:
Write a row of Flash memory with 16-bit data. The length of a row is
_FLASH_ROW words. The upper byte of each destination word is filled
with 0xFF. Note that the row must be erased before any write can be
successful.
Include:
<libpic30.h>
Prototype:
void _write_flash16(_prog_addressT dst,
int *src);
Argument:
dst
*src
Return Value:
None.
Remarks:
None.
Default Behavior:
Write a row of Flash memory with 16-bit data.
File:
flash_helper.s
 2004-2014 Microchip Technology Inc.
destination memory address
points to the storage location of data to be written
DS50001456J-page 211
16-Bit Language Tools Libraries
_write_flash24
Description:
Write a row of Flash memory with 24-bit data. The length of a row is
_FLASH_ROW words. Note that the row must be erased before any write
can be successful.
Include:
<libpic30.h>
Prototype:
void _write_flash24(_prog_addressT dst,
long *src);
Argument:
dst
*src
Return Value:
None.
Remarks:
None.
Default Behavior:
Write a row of Flash memory with 24-bit data.
File:
flash_helper.s
destination memory address
points to the storage location of data to be written
_write_flash_word16
Description:
Write a word of Flash memory with 16-bit data. The upper byte of the
destination word is filled with 0xFF. Note that the word must be erased
before any write can be successful. This function is currently available
only for PIC24F devices (excluding PIC24FXXKA MCUs).
Include:
<libpic30.h>
Prototype:
void _write_flash_word16(_prog_addressT dst,
int dat);
Argument:
dst
dat
Return Value:
None.
Remarks:
None.
Default Behavior:
Write a word of Flash memory with 16-bit data for most PIC24 devices.
File:
flash_helper.s
destination memory address
integer data to be written
_write_flash_word24
DS50001456J-page 212
Description:
Write a word of Flash memory with 24-bit data. Note that the word must
be erased before any write can be successful. This function is currently
available only for PIC24F devices (excluding PIC24FXXKA MCUs).
Include:
<libpic30.h>
Prototype:
void _write_flash_word24(_prog_addressT dst,
long dat);
Argument:
dst
dat
Return Value:
None.
Remarks:
None.
Default Behavior:
Write a word of Flash memory with 24-bit data for most PIC24 devices.
File:
flash_helper.s
destination memory address
integer data to be written
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Support Functions
_write_flash_word32
Description:
Write two words of FLASH memory with 16 bits of data per word. The
16 bits are written to the low 16 bits of the word. Word writes are supported dsPIC33E and PIC24E devices. The row address is specified
with type _prog_addressT. Note that the location must be erased
before any write can be successful.
This function is currently disabled for devices subject to the Device ID
errata as described in DS-80444, DS-80446, or DS-80447 (#32).
Include:
<libpic30.h>
Prototype:
void _write_flash_word32(_prog_addressT dst,
int dat1, int dat2);
Argument:
dst
dat1, dat2
Return Value:
None.
Remarks:
None.
Default Behavior:
Write two words of Flash memory with 16-bit data for most
dsPIC33E/PIC24E devices.
File:
flash_helper.s
destination memory address
integer data to be written
_write_flash_word48
Description:
Write two words of FLASH memory with 24 bits of data per word. Word
writes are supported 33E and 24E devices. The row address is specified with type _prog_addressT. Note that the location must be erased
before any write can be successful.
This function is currently disabled for devices subject to the Device ID
errata as described in DS-80444, DS-80446, or DS-80447 (#32).
Include:
<libpic30.h>
Prototype:
void _write_flash_word48(_prog_addressT dst,
int dat1, int dat2);
Argument:
dst
dat1, dat2
Return Value:
None.
Remarks:
None.
Default Behavior:
Write two words of Flash memory with 48-bit data for most
dsPIC33E/PIC24E devices.
File:
flash_helper.s
 2004-2014 Microchip Technology Inc.
destination memory address
integer data to be written
DS50001456J-page 213
16-Bit Language Tools Libraries
Example of Use
#include "libpic30.h"
#include "p24Fxxxx.h"
int __attribute__((space(prog),aligned(_FLASH_PAGE*2)))
dat[_FLASH_PAGE];
int main()
{
int i;
int
source1[_FLASH_ROW];
long source2[_FLASH_ROW];
_prog_addressT p;
for (i = 0; i < _FLASH_ROW; ) {
source1[i] = i;
source2[i] = i++;
}
/* initialize some data */
_init_prog_address(p, dat);
/* get address in program space */
_erase_flash(p);
/* erase a page */
_write_flash16(p, source1);
/* write first row with 16-bit data */
#if defined (__dsPIC30F__)
_erase_flash(p);
#else
p += (_FLASH_ROW * 2);
#endif
_write_flash24(p, source2);
/* on dsPIC30F, only 1 row per page */
/* advance to next row */
/* write second row with 24-bit data */
}
DS50001456J-page 214
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Support Functions
Example of Use – PIC24FXXKA MCUs
#include "libpic30.h"
#include "p24Fxxxx.h"
/* should use <> here */
int __attribute__((space(prog),aligned(_FLASH_2ROWS*2)))
dat[_FLASH_2ROWS];
int main()
{
int i;
int
source1[_FLASH_ROW];
long source2[_FLASH_ROW];
_prog_addressT p;
for (i = 0; i < _FLASH_ROW; ) {
source1[i] = i;
source2[i] = i++;
}
_init_prog_address(p, dat);
_erase_flash(p, _FLASH_2ROWS);
_write_flash16(p, source1);
p += (_FLASH_ROW * 2);
_write_flash24(p, source2);
/* get address in program
space */
/* erase two rows */
/* write first row with
16-bit data */
/* advance to next row */
/* write second row with
24-bit data */
}
 2004-2014 Microchip Technology Inc.
DS50001456J-page 215
16-Bit Language Tools Libraries
4.8
FUNCTIONS FOR SPECIALIZED COPYING AND INITIALIZATION
These functions support specialized data copying and initialization.
_memcpy_p2d16
Description:
Copy 16 bits of data from each address in program memory to data
memory. The next unused source address is returned.
Include:
<libpic30.h>
Prototype:
_prog_addressT _memcpy_p2d16(char *dest,
_prog_addressT src, unsigned int len);
Argument:
*dest
src
len
Return Value:
The next unused source address.
Remarks:
None.
Default Behavior:
Copy 16 bits of data from each address in program memory to data
memory.
File:
memcpy_helper.s
pointer to destination memory address
address of data to be written
length of program memory
_memcpy_p2d24
Description:
Copy 24 bits of data from each address in program memory to data
memory. The next unused source address is returned.
Include:
<libpic30.h>
Prototype:
_prog_addressT _memcpy_p2d24(char *dest,
_prog_addressT src, unsigned int len);
Argument:
*dest
src
len
Return Value:
The next unused source address.
Remarks:
None.
Default Behavior:
Copy 24 bits of data from each address in program memory to data
memory.
File:
memcpy_helper.s
pointer to destination memory address
address of data to be written
length of program memory
_strncpy_p2d16
DS50001456J-page 216
Description:
Copy 16 bits of data from each address in program memory to data
memory. The operation terminates early if a NULL char is copied. The
next unused source address is returned.
Include:
<libpic30.h>
Prototype:
_prog_addressT _strncpy_p2d16(char *dest,
_prog_addressT src, unsigned int len);
Argument:
*dest
src
len
Return Value:
The next unused source address.
Remarks:
None.
Default Behavior:
Copy 16 bits of data from each address in program memory to data
memory.
File:
memcpy_helper.s
pointer to destination memory address
address of data to be written
length of program memory
 2004-2014 Microchip Technology Inc.
Standard C Libraries - Support Functions
_strncpy_p2d24
Description:
Copy 24 bits of data from each address in program memory to data
memory. The operation terminates early if a NULL char is copied. The
next unused source address is returned.
Include:
<libpic30.h>
Prototype:
_prog_addressT _strncpy_p2d24(char *dest,
_prog_addressT src, unsigned int len);
Argument:
*dest
src
len
Return Value:
The next unused source address.
Remarks:
None.
Default Behavior:
Copy 24 bits of data from each address in program memory to data
memory.
File:
memcpy_helper.s
pointer to destination memory address
address of data to be written
length of program memory
_init_prog_address
Description:
A macro that is used to initialize variables of type, _prog_addressT.
These variables are not equivalent to C pointers.
Include:
<libpic30.h>
Prototype:
_init_prog_address(a,b);
Argument:
a
b
Return Value:
N/A
Remarks:
None.
Default Behavior:
Initialize variable to specified value.
File:
libpic30.c
 2004-2014 Microchip Technology Inc.
variable of type _prog_addressT
initialization value for variable a
DS50001456J-page 217
16-Bit Language Tools Libraries
Example of Use
#include "stdio.h"
#include "libpic30.h"
void display_mem(char *p, unsigned int len) {
int i;
for (i = 0; i < len; i++) {
printf(" %d", *p++);
}
printf("\n");
}
char __attribute__((space(prog))) dat[] =
{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
char buf[10];
int main() {
int i;
_prog_addressT p;
/* method 1 */
_init_prog_address(p, dat);
(void) _memcpy_p2d16(buf, p, 10);
display_mem(buf,10);
/* method 2 */
_init_prog_address(p, dat);
p = _memcpy_p2d16(buf, p, 4);
p = _memcpy_p2d16(&buf[4], p, 6);
display_mem(buf,10);
}
DS50001456J-page 218
 2004-2014 Microchip Technology Inc.
16-BIT LANGUAGE TOOLS
LIBRARIES
Chapter 5. Fixed-Point Math Functions
5.1
INTRODUCTION
Fixed-point library math functions are contained in the files libq-omf.a (standard) and
libq-dsp-omf.a (DSP), where omf will be coff or elf depending upon the selected
object module format. The header file is named libq.h, and is the same for standard
or DSP versions of the library. Linker options -lq (standard and DSP) and -lq-dsp
(DSP only) must be used when linking the respective libraries.
5.1.1
Assembly Code Applications
A free version of the math functions library and header file is available from the
Microchip web site.
5.1.2
C Code Applications
The MPLAB XC16 C Compiler install directory (Section 1.1.1 “Compiler Installation
Locations”) contains the following subdirectories with library-related files:
• lib – standard C library files
• support\h – header files for libraries
In addition, there is a file, ResourceGraphs.pdf, which contains diagrams of resources
used by each function, located in lib.
5.1.3
Chapter Organization
This chapter is organized as follows:
• Overview of Fixed-Point Data Formats
• Using the Fixed-Point Libraries
• <libq.h> mathematical functions
 2004-2014 Microchip Technology Inc.
DS50001456J-page 219
16-Bit Language Tools Libraries
5.2
OVERVIEW OF FIXED-POINT DATA FORMATS
The integer data is encoded as its two’s compliment to accommodate both positive and
negative numbers in binary format. The two’s compliment can be represented using
integer format or the fractional format.
5.2.1
Integer Format
The integer format data is represented as a signed two’s complement value, where the
Most Significant bit is defined as a sign bit. The range of an N-bit two’s complement
integer is -2N-1 to 2N-1-1 with a resolution of 1. For a 16-bit integer, the data range is
-32768 (0x8000) to +32767 (0x7FFF) with a resolution of 1. For a 32-bit integer, the
data range is -2,147,483,648 (0x8000 0000) to +2,147,483,647 (0x7FFF FFFF) with a
resolution of 1.
5.2.2
Fractional Format
The fractional data format (Qn.m) has integral part (n) and fractional part (m) and the
Most Significant bit represents the sign, thus consisting of (m+n+1) bits. It represents
a signed two’s complement value. Qn.m format data has a range of [-2n, (2n-2-m)] with
2-m resolution.
The binary representation of an N-bit (m+n+1 bits) number in Qn.m is shown in
Figure 5-1. The value is given by the equation shown in Figure 5-2.
FIGURE 5-1:
BINARY REPRESENTATION
b m
 n b m  n  1 ... b m .b m  1 ... b 1 b o
N 1
FIGURE 5-2:
EQUATION VALUE
N2
Value  b N 1 2   bl 2
n
l m
l0
5.2.2.1
Q15 (1.15) FORMAT
In Q15 format, the Most Significant bit is defined as a sign bit and the radix point is
implied to lie just after the sign bit followed by the fractional value. This format is
commonly referred to as 1.15 or Q15 format, where 1 is the number of bits used to represent the integer portion of the number, and 15 is the number of bits used to represent
the fractional portion. The range of an N-bit two’s complement fraction with this implied
radix point is -1.0 to (1 - 21-N). For a 16-bit fraction, the 1.15 data range is -1.0 (0x8000)
to +0.999969482 (0x7FFF) with a precision of 3.05176x10-5.
FIGURE 5-3:
FRACTIONAL FORMAT (16 BITS)
Bit Position
15
0
14
-1
-2
2
0
or
-1
1
2
13
2
-2
1
4
12
2
-3
1
8
11
2
-4
1
16
10
2
-5
1
32
9
2
-6
1
64
8
2
-7
1
128
7
2
-8
1
256
6
2
-9
5
4
3
2
1
-10
-11
-12
-13
-14
2
2
2
2
2
0
2
-15
1
1
1
1
1
1
1
512 1024 2048 4096 8192 16384 32768
Implied Radix (Decimal) Point
Bit Value
DS50001456J-page 220
 2004-2014 Microchip Technology Inc.
Fixed-Point Math Functions
The following table shows the conversion of a two’s complement 16-bit integer +24576
to Q15 value +0.75.
TABLE 5-1:
CONVERSION OF A TWO’S COMPLEMENT 16-BIT INTEGER TO
Q15
Binary
Dec
0
0x
Q15
(-215
)
0
0
0 x (-2 )
0


1
1 x 214
16384
1 x 2-1
0.5
1
1x
213
8192
1 x 2-2
0.25
0
0 x 212
0
0 x 2-3
0
0
11
0
0 x 2-4
0
210
0
0x2
-5
0
0
0 x 29
0
0 x 2-6
0
0
0x2
8
0
0x2
-7
0
0
0 x 27
0
0 x 2-8
0
0
0x2
6
0
0x2
-9
0
0
0 x 25
0
0 x 2-10
0
0
0x
24
0
0x
2-11
0
0
0 x 23
0
0 x 2-12
0
0
0x2
2
0
0x
2-13
0
0
0 x 21
0
0 x 2-14
0
0
20
0
2-15
0x2
0
0x
0x
SUM
0x
+24576
SUM
0
+0.75
 - Radix Point
5.2.2.2
Q15.16 FORMAT
In the Q15.16 format, the Most Significant bit is defined as a sign bit followed by 16 bits
of the integral part. The radix point is implied to lie just after the integral part, followed
by 16 bits of the fractional value. This format is commonly referred to as Q15.16 format.
The range of Q15.16 numbers is from -32768.0 (0x8000 0000) to
+32767.9999847412109375 (0x7FFF FFFF) and has a precision of 2-16.
FIGURE 5-4:
FRACTIONAL FORMAT (32 BITS)
Bit Position
31
-2
30
15
2
0
or
-1
14
29
2
13
28
2
12
27
2
11
26
2
10
25
2
9
Sign Bit
24
2
8
23
2
22
7
2
6
21
2
5
20
2
4
19
2
3
18
2
2
17
2
1
16
2
0
Integral Part
Bit Position
15
14
13
12
11
10
-1
-2
-3
-4
-5
-6
2
2
1
2
1
4
2
1
8
2
1
16
2
1
32
2
1
64
9
2
-7
1
128
8
2
-8
1
256
7
2
-9
2
6
5
4
3
2
-10
-11
-12
-13
-14
2
2
2
2
1
2
-15
0
2
-16
1
1
1
1
1
1
1
1
512 1024 2048 4096 8192 16384 32768 65536
Implied Radix (Decimal) Point
Fractional Part
 2004-2014 Microchip Technology Inc.
DS50001456J-page 221
16-Bit Language Tools Libraries
The following table shows the conversion of a two’s complement 32-bit integer,
-715827882 to Q15.16 value -10922.6666564941.
TABLE 5-2:
CONVERSION OF A TWO’S COMPLEMENT 32-BIT INTEGER TO
Q15.16
Binary
Dec
Q15.16
(-231
)
-2147483648
1 x (-2 )
-32768
1
1 x 230
1073741824
1 x 214
16384
0
29
0x2
0
13
0
1
1 x 228
268435456
1 x 212
4096
0
0 x 227
0
0 x 211
0
1
26
1x2
67108864
1 x 210
1024
0
0 x 225
0
0 x 29
0
1
24
1x2
16777216
1 x 28
256
0
0 x 223
0
0 x 27
0
1
1x
222
4194304
1 x 26
64
0
0 x 221
0
0 x 25
0
1
20
1x2
1048576
1 x 24
16
0
0 x 219
0
0 x 23
0
1
218
262144
1 x 22
4
0
17
0x2
0
21
0
1
1 x 216
65536
1 x 20
1
0
0 x 215
0
0 x 2-1
0
1
1x
214
16384
2-2
0.25
0
0 x 213
0
0 x 2-3
0
1
12
1x2
4096
2-4
0.0625
0
0 x 211
0
0 x 2-5
0
1
210
1024
2-6
0.015625
0
0 x 29
0
0 x 2-7
0
1
1x
28
256
2-8
0.00390625
0
0 x 27
0
0 x 2-9
0
1
1x2
6
64
2-10
0.000976563
0
0 x 25
0
0 x 2-11
0
1
1x
24
16
-12
0.000244141
0
0 x 23
0
0 x 2-13
0
1
1x
22
4
1x
2-14
6.10352E-05
1
1 x 21
2
1 x 2-15
3.01576E-05
0
0
0
2-16
1
1x
1x
15
0x2
0x

1x
0x2
SUM
-715827882

1x
1x
1x
1x
1x
1x2
0x
SUM
0
-10922.6666564941
 - Radix Point
DS50001456J-page 222
 2004-2014 Microchip Technology Inc.
Fixed-Point Math Functions
5.2.3
Integer - Fractional Format Mapping
The same twos complement N-bit word may represent an integer format value or a fractional format value. For example., the 16-bit integer range [-32768, +32767] format maps
to Q15 range of [-1.0, +0.999969482]. Figure 5-5 shows the mapping between these
formats.
FIGURE 5-5:
MAPPING BETWEEN 16-BIT INTEGER FORMAT AND Q15
FRACTIONAL FORMAT
Integer
-32768
-24576
-16384
-8192
0
8192
16384
24576
32767
-1.0000
-0.7500
-0.5000
-0.2500
0
0.2500
0.5000
0.7500
0.9999
Fractional Values
A similar relationship exists between the 32-bit integer format and the Q15.16 format,
where the integer range [-2147483648, +2147483647] is mapped to the Q15.16 range
[-32768.0, +32767.9999847412109375].
FIGURE 5-6:
MAPPING BETWEEN 32-BIT INTEGER FORMAT AND Q15.16
FORMAT
Integer
-2147483648 -1431655764
-32768.0
5.2.4
-715827882
0
715827882
1431655764
2147483647
0
+32767.9999847
-10922.6666564941
+10922.6666564941
-21845.3333129882
+21845.3333129882
Q15.16 Values
libq Library and Fixed-Point Data Format
The functions in the libq library use the fixed-point data format. The parameters
passed and the results generated by the functions are fractional in nature. There are
two similar sets of math functions which perform the same math operations. One set
supports Q15 operands and the other supports Q15.16 operands. Q15.16 operand
functions, naturally, have better precision and range compared to Q15 operand
functions.
5.3
USING THE FIXED-POINT LIBRARIES
Building an application which utilizes the fixed-point libraries requires two types of files:
header files and library files.
5.3.1
Header Files
All standard C library entities are declared or defined in one or more standard headers
(see list in Section 5.1.3 “Chapter Organization”). To make use of a library entity in
a program, write an include directive that names the relevant standard header.
The contents of a standard header are included by naming them in an include directive,
as in:
#include <libq.h> /* include fixed-point library */
The standard headers can be included in any order. Do not include a standard header
within a declaration. Do not define macros that have the same names as keywords
before including a standard header.
A standard header never includes another standard header.
 2004-2014 Microchip Technology Inc.
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16-Bit Language Tools Libraries
5.3.2
Library Files
The archived library files contain all the individual object files for each library function.
When linking an application, the library file (libq-omf.a or libq-dsp-omf.a) must be
provided as an input to the linker (using the --library or -l linker option), such that
the functions used by the application may be linked into the application. Also, linker
options -lq and -lq-dsp must be used when linking the respective libraries.
A typical C application will require three library files: libc-omf.a, libm-omf.a and
libpic30-omf.a (see Section 1.2 “OMF-Specific Libraries/Start-up Modules” for
more on OMF-specific libraries). These libraries will be included automatically if linking
is performed using the compiler.
5.3.3
Function Naming Conventions
Signed fixed-point types are defined as follows:
Qn_m
where:
• n is the number of data bits to the left of the radix point
• m is the number of data bits to the right of the radix point
Note:
A sign bit is implied.
For convenience, short names are also defined:
Exact Name
# Bits Required
Short Name
_Q0_15
16
_Q15
_Q15_16
32
_Q16
In this document, the terms Q15.16 and Q16 are used interchangeably; however, both
imply Q15.16 format. Functions in the library are prefixed with the type of the return
value. For example, _Q15acos returns a Q15 value equal to the arc cosine of its argument.
Argument types do not always match the return type. Refer to the function prototype
for a specification of its arguments.
In cases where the return value is not a fixed-point type, the argument type is appended
to the function name. For example, function _itoaQ15 accepts a type
Q15 argument.
In cases where two versions of a function are provided with the same return type but
different argument types, the argument type is appended to the function name. For
example:
Function Name
DS50001456J-page 224
Return Type
Argument Type
_Q16reciprocalQ15
_Q16
_Q15
_Q16reciprocalQ16
_Q16
_Q16
 2004-2014 Microchip Technology Inc.
Fixed-Point Math Functions
5.4
<LIBQ.H> MATHEMATICAL FUNCTIONS
The header file libq.h consists of macro definitions and various functions that
calculate fixed-point mathematical operations.
5.4.1
Q15 Functions
Many functions in this section use fixed-point Q15 (1.15) format. For each function, the
entire range may not be used.
_Q15abs
Description:
The function finds the absolute value of a Q15 value.
Include:
<libq.h>
Prototype:
_Q15 _Q15abs(_Q15 x);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 32767.
Return Value:
This function returns the absolute value of x in Q15 format. The value
ranges from 0 to 32767.
_Q15acos
Description:
This function finds the arc cosine of a Q15 value.
Include:
<libq.h>
Prototype:
_Q15 _Q15acos(_Q15 x);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from 17705 to 32767.
Return Value:
This function returns the arc cosine of x in Q15 format. The value
ranges from 256 to 32767.
_Q15acosByPI
Description:
This function finds the arc cosine of a Q15 value and then divides by
PI ().
Include:
<libq.h>
Prototype:
_Q15 _Q15acosByPI(_Q15 x);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 32767.
Return Value:
This function returns the arc cosine of x, divided by PI, in Q15 format.
The value ranges from 82 to 32767.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 225
16-Bit Language Tools Libraries
_Q15add
Description:
This function finds the sum value of two Q15 values. The function takes
care of saturation during overflow and underflow occurrences.
Include:
<libq.h>
Prototype:
_Q15 _Q15add(_Q15 x, _Q15 y);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 32767.
y a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 32767.
Return Value:
This function returns the sum of x and y in Q15 format. The value
ranges from -32768 to 32767.
_Q15asin
Description:
This function finds the arc sine of a Q15 value.
Include:
<libq.h>
Prototype:
_Q15 _Q15asin(_Q15 x);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -27573 to 27573.
Return Value:
This function returns the arc sine of x in Q15 format. The value ranges
from -32768 to 32767.
_Q15asinByPI
Description:
This function finds the arc sine of a Q15 value and then divides by
PI ().
Include:
<libq.h>
Prototype:
_Q15 _Q15asinByPI(_Q15 x);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 32767.
Return Value:
This function returns the arc sine of x, divided by PI, in Q15 format. The
value ranges from -16384 to 16303.
_Q15atan
DS50001456J-page 226
Description:
This function finds the arc tangent of a Q15 value.
Include:
<libq.h>
Prototype:
_Q15 _Q15atan(_Q15 x);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 32767.
Return Value:
This function returns the arc tangent of x in Q15 format. The value
ranges from -25736 to 25735.
 2004-2014 Microchip Technology Inc.
Fixed-Point Math Functions
_Q15atanByPI
Description:
This function finds the arc tangent of a Q15 value and then divides by
PI ().
Include:
<libq.h>
Prototype:
_Q15 _Q15atanByPI(_Q15 x);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 32767.
Return Value:
This function returns the arc tangent of x, divided by PI, in Q15 format.
The value ranges from -8192 to 8192.
_Q15atanYByX
Description:
This function finds the arc tangent of a Q15 value divided by a second
Q15 value.
Include:
<libq.h>
Prototype:
_Q15 _Q15atanYByX(_Q15 x, _Q15 y);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 32767.
y a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 32767.
Return Value:
This function returns the arc tangent of y divided by x in Q15 format.
The value ranges from -25736 to 25735.
_Q15atanYByXByPI
Description:
This function finds the arc tangent of a Q15 value divided by a second
Q15 value and then divides the result by PI ().
Include:
<libq.h>
Prototype:
_Q15 _Q15atanYByXByPI(_Q15 x, _Q15 y);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 32767.
y a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 32767.
Return Value:
This function returns the arc tangent of y divided by x, divided by PI, in
Q15 format. The value ranges from -8192 to 8192.
_Q15atoi
Description:
This function takes a string which holds the ASCII representation of
decimal digits and converts it into a single Q15 number.
Note: The decimal digit should not be beyond the range: -32768 to
32767.
Include:
<libq.h>
Prototype:
_Q15 _Q15atoi(const char *s);
Argument:
s
Return Value:
This function returns the integer equivalent of s in Q15 format, which
range is from -32768 to 32767.
 2004-2014 Microchip Technology Inc.
a buffer holding the ASCII values of each decimal digit.
DS50001456J-page 227
16-Bit Language Tools Libraries
_Q15cos
Description:
This function finds the cosine of a Q15 value.
Include:
<libq.h>
Prototype:
_Q15 _Q15cos(_Q15 x);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 32767.
Return Value:
This function returns the cosine of x in Q15 format. The value ranges
from 17705 to 32767.
_Q15cosPI
Description:
This function finds the cosine of PI () times a Q15 value.
Include:
<libq.h>
Prototype:
_Q15 _Q15cosPI(_Q15 x);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 32767.
Return Value:
This function returns the cosine of PI times x in Q15 format. The value
ranges from -32768 to 32767.
_Q15exp
Description:
This function finds the exponential value of a Q15 value.
Include:
<libq.h>
Prototype:
_Q15 _Q15exp(_Q15 x);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 0.
Return Value:
This function returns the exponent value of x in Q15 format. The value
ranges from 12055 to 32767.
_Q15ftoi
DS50001456J-page 228
Description:
This function converts a single precision floating-point value into its
corresponding Q15 value.
Include:
<libq.h>
Prototype:
_Q15 _Q15ftoi(float x);
Argument:
x a floating-point equivalent number. The corresponding
floating-point range is -1 to 0.99996.
Return Value:
This function returns a fixed-point number in Q15 format. The value
ranges from -32768 to 32767.
 2004-2014 Microchip Technology Inc.
Fixed-Point Math Functions
_itoaQ15
Description:
This function converts each decimal digit of a Q15 value to its representation in ASCII. For example, 1 is converted to 0x31, which is the ASCII
representation of 1.
Include:
<libq.h>
Prototype:
void _itoaQ15(_Q15 x, char *s);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 32767.
s a buffer holding values in ASCII, at least 8 characters long.
Return Value:
None.
_itofQ15
Description:
This function converts a Q15 value into its corresponding floating-point
value.
Include:
<libq.h>
Prototype:
float _itofQ15(_Q15 x);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 32767.
Return Value:
This function returns a floating-point equivalent number. The
corresponding floating-point range is -1 to 0.99996.
_Q15log
Description:
This function finds the natural log of a Q15 value.
Include:
<libq.h>
Prototype:
_Q15 _Q15log(_Q15 x);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from 12055 to 32767.
Return Value:
This function returns the natural log of x in Q15 format. The value
ranges from -32768 to -1.
_Q15log10
Description:
This function finds the log (base 10) of a Q15 value.
Include:
<libq.h>
Prototype:
_Q15 _Q15log10(_Q15 x);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from 3277 to 32767.
Return Value:
This function returns the log of x in Q15 format. The value ranges from
-32768 to 0.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 229
16-Bit Language Tools Libraries
_Q15neg
Description:
This function negates a Q15 value with saturation. The value is
saturated in the case where the input is -32768.
Include:
<libq.h>
Prototype:
_Q15 _Q15neg(_Q15 x);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 32767.
Return Value:
This function returns -x in Q15 format. The value ranges from -32768 to
32767.
_Q15norm
Description:
This function finds the normalized value of a Q15 value.
Include:
<libq.h>
Prototype:
_Q15 _Q15norm(_Q15 x);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 32767.
Return Value:
This function returns the square root of x in Q15 format. The value
ranges from 16384 to -32767 for a positive number and -32768 to
-16384 for a negative number.
_Q15power
Description:
This function finds the power result given the base value and the power
value in Q15 format.
Include:
<libq.h>
Prototype:
_Q15 _Q15power(_Q15 x, _Q15 y);
Argument:
x a fixed-point number in Q15 format, which ranges from 1 to 215-1.
The value of this argument ranges from 1 to 32767.
y a fixed-point number in Q15 format, which ranges from 1 to 215-1.
The value of this argument ranges from 1 to 32767.
Return Value:
This function returns x to the power of y in Q15 format. The value
ranges from 1 to 32767.
_Q15random
DS50001456J-page 230
Description:
This function generates a random number in the range from -32768 to
32767. The random number generation is periodic with period 65536.
The function uses the _Q15randomSeed variable as a random seed
value.
Include:
<libq.h>
Prototype:
_Q15 _Q15random(void);
Argument:
None.
Return Value:
This function returns a random number in Q15 format. The value
ranges from -32768 to 32767.
 2004-2014 Microchip Technology Inc.
Fixed-Point Math Functions
_Q15shl
Description:
This function shifts a Q15 value by num bits, to the left if num is positive
or to the right if num is negative. The function takes care of saturating
the result, in case of underflow or overflow.
Include:
<libq.h>
Prototype:
_Q15 _Q15shl(_Q15 x, short num);
Argument:
x
a fixed-point number in Q15 format, which ranges from -215 to
15
2 -1. The value of this argument ranges from -32768 to 32767.
num an integer number, which ranges from -15 to 15.
Return Value:
This function returns the shifted value of x in Q15 format. The value
ranges from -32768 to 32767.
_Q15shlNoSat
Description:
This function shifts a Q15 value by num bits, to the left if num is positive
or to the right if num is negative. The function sets the
_Q15shlSatFlag variable in case of underflow or overflow but does
not take care of saturation.
Include:
<libq.h>
Prototype:
_Q15 _Q15shlNoSat(_Q15 x, short num);
Argument:
x
a fixed-point number in Q15 format, which ranges from -215 to
15-1. The value of this argument ranges from -32768 to 32767.
2
num an integer number, which ranges from -15 to 15.
Return Value:
This function returns the shifted value of x in Q15 format. The value
ranges from -32768 to 32767.
_Q15shr
Description:
This function shifts a Q15 value by num bits, to the right if num is
positive or to the left if num is negative. The function takes care of
saturating the result, in case of underflow or overflow.
Include:
<libq.h>
Prototype:
_Q15 _Q15shr(_Q15 x, short num);
Argument:
x
a fixed-point number in Q15 format, which ranges from -215 to
15-1. The value of this argument ranges from -32768 to 32767.
2
num an integer number, which ranges from -15 to 15.
Return Value:
This function returns the shifted value of x in Q15 format. The value
ranges from -32768 to 32767.
_Q15shrNoSat
Description:
This function shifts a Q15 value by num bits, to the right if num is
positive or to the left if num is negative. The function sets the
_Q15shrSatFlag variable in case of underflow or overflow but does
not take care of saturation.
Include:
<libq.h>
Prototype:
_Q15 _Q15shrNoSat(_Q15 x, short num);
Argument:
x
a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 32767.
num an integer number, which ranges from -15 to 15.
Return Value:
This function returns the shifted value of x in Q15 format. The value
ranges from -32768 to 32767.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 231
16-Bit Language Tools Libraries
_Q15sin
Description:
This function finds the sine of a Q15 value.
Include:
<libq.h>
Prototype:
_Q15 _Q15sin(_Q15 x);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 32767.
Return Value:
This function returns the sine of x in Q15 format. The value ranges from
-27573 to 27573.
_Q15sinPI
Description:
This function finds the sine of PI () times a Q15 value.
Include:
<libq.h>
Prototype:
_Q15 _Q15sinPI(_Q15 x);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 32767.
Return Value:
This function returns the sine of PI times x in Q15 format. The value
ranges from -32768 to 32767.
_Q15sinSeries
DS50001456J-page 232
Description:
Generates the sine series with the given normalizing frequency, f, and
the given number of samples, num, starting from start. Stores the
result in buffer, buf.
Include:
<libq.h>
Prototype:
short _Q15sinSeries(_Q15 f, short start, short num,
_Q15 *buf);
Argument:
f
a fixed-point number in Q15 format, which ranges from 0 to
(231-1). The valid range of values for this argument is from -16384 to
16384. The argument represents the Normalizing frequency.
start a fixed-point number in Q16 format, which ranges from 0 to
(231-1). The valid range of values for this argument is from 1 to 32767.
This argument represents the Starting Sample number in the Sine
Series.
num a fixed-point number in Q16 format, which ranges from 0 to
(231-1). The valid range of values for this argument is from 1 to 32767.
This argument represents the Number of Sine Samples the function is
called to generate.
Note: num should not be more than 16383 for dsPIC and 32767 for PIC
devices.
buf a pointer to the buffer where the generated sine samples would
get copied into.
Return Value:
This function returns num, the number of generated sine samples.
 2004-2014 Microchip Technology Inc.
Fixed-Point Math Functions
_Q15sqrt
Description:
This function finds the square root of a Q15 value.
Include:
<libq.h>
Prototype:
_Q15 _Q15sqrt(_Q15 x);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from 1 to 32767.
Return Value:
This function returns the square root of x in Q15 format. The value
ranges from 1 to 32767.
_Q15sub
Description:
This function finds the difference of two Q15 values. The function takes
care of saturation during overflow and underflow occurrences.
Include:
<libq.h>
Prototype:
_Q15 _Q15sub(_Q15 x,_Q15 y);
Argument:
x
a fixed-point number in Q15 format, which ranges from -215 to
15
2 -1. The value of this argument ranges from -32768 to 32767.
y
a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 32767.
Return Value:
This function returns x minus y in Q15 format. The value ranges from
-32768 to 32767.
_Q15tan
Description:
This function finds the tangent of a Q15 value.
Include:
<libq.h>
Prototype:
_Q15 _Q15tan(_Q15 x);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -25736 to 25735.
Return Value:
This function returns the tangent of x in Q15 format. The value ranges
from -32768 to 32767.
_Q15tanPI
Description:
This function finds the tangent of PI () times a Q15 value.
Include:
<libq.h>
Prototype:
_Q15 _Q15tanPI(_Q15 x);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 32767.
Return Value:
This function returns the tangent of PI times x in Q15 format. The value
ranges from -32768 to 32767.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 233
16-Bit Language Tools Libraries
5.4.2
Q16 Functions
Many functions in this section use fixed-point Q16 (15.16) format. For each function,
the entire range may not be used.
_Q16acos
Description:
This function finds the arc cosine of a Q16 value.
Include:
<libq.h>
Prototype:
_Q16 _Q16acos(_Q16 x);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from -65566 to 65536.
Return Value:
This function returns the arc cosine of x in Q16 format. The value
ranges from -205887 to 205887.
_Q16acosByPI
Description:
This function finds the arc cosine of a Q16 value and then divides by
PI ().
Include:
<libq.h>
Prototype:
_Q16 _Q16acosByPI(_Q16 x);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from -65536 to 65536.
Return Value:
This function returns the arc cosine of x, divided by PI, in Q16 format.
The value ranges from -65536 to 65536.
_Q16asin
Description:
This function finds the arc sine of a Q16 value.
Include:
<libq.h>
Prototype:
_Q16 _Q16asin(_Q16 x);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from -65566 to 65536.
Return Value:
This function returns the arc sine of x in Q16 format. The value ranges
from -102944 to 102944.
_Q16asinByPI
DS50001456J-page 234
Description:
This function finds the arc sine of a Q16 value and then divides by
PI ().
Include:
<libq.h>
Prototype:
_Q16 _Q16asinByPI(_Q16 x);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from -65536 to 65536.
Return Value:
This function returns the arc sine of x, divided by PI, in Q16 format. The
value ranges from-65536 to 65536.
 2004-2014 Microchip Technology Inc.
Fixed-Point Math Functions
_Q16atan
Description:
This function finds the arc tangent of a Q16 value.
Include:
<libq.h>
Prototype:
_Q16 _Q16atan(_Q16 x);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from -2147483648 to 2147483647.
Return Value:
This function returns the arc tangent of x in Q16 format. The value
ranges from -2147483648 to 2147483647.
_Q16atanByPI
Description:
This function finds the arc tangent of a Q16 value and then divides by
PI ().
Include:
<libq.h>
Prototype:
_Q16 _Q16atanByPI(_Q16 x);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from -2147483648 to 2147483647.
Return Value:
This function returns the arc tangent of x, divided by PI, in Q16 format.
The value ranges from -2147483648 to 2147483647.
_Q16atanYByX
Description:
This function finds the arc tangent of y divided by x.
Include:
<libq.h>
Prototype:
_Q16 _Q16atanYByX(_Q16 x, _Q16 y);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from -2147483648 to 2147483647. This forms the x input.
y a fixed-point number in Q16 format. The value of this argument
ranges from -2147483648 to 2147483647. This forms the y input.
Return Value:
This function returns the arc tangent of y, divided by x, in Q16 format.
The value ranges from -2147483648 to 2147483647.
_Q16atanYByXByPI
Description:
This function finds the arc tangent of the 32-bit input, y, divided by x,
and then divides by PI ().
Include:
<libq.h>
Prototype:
_Q16 _Q16atanYByXByPI(_Q16 x, _Q16 y);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from -2147483648 to 2147483647. This forms the x input.
y a fixed-point number in Q16 format. The value of this argument
ranges from -2147483648 to 2147483647. This forms the y input.
Return Value:
This function returns the arc tangent y divided by x, divided by PI, in
Q16 format. The value ranges from -2147483648 to 2147483647.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 235
16-Bit Language Tools Libraries
_Q16cos
Description:
This function finds the cosine of a Q16 value.
Include:
<libq.h>
Prototype:
_Q16 _Q16cos(_Q16 x);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from -2147483648 to 2147483647.
Return Value:
This function returns the cosine of x in Q16 format. The value ranges
from -65566 to 65536.
_Q16cosPI
Description:
This function finds the cosine of PI () times a Q16 value.
Include:
<libq.h>
Prototype:
_Q16 _Q16cosPI(_Q16 x);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from -2147483648 to 2147483647.
Return Value:
This function returns the cosine of PI times x in Q16 format. The value
ranges from -65536 to 65536.
_Q16div
Description:
This function returns the quotient of its arguments.
Include:
<libq.h>
Prototype:
_Q16 _Q16mpy(_Q16 dividend, _Q16 divisor);
Argument:
dividend a fixed-point number in Q16 format. The value of this argument ranges from 0 to 2147483647.
divisor a fixed-point number in Q16 format. The value of this argument ranges from 0 to 2147483647.
Return Value:
This function returns the quotient of its arguments. The value ranges
from 0 to 2147483647..
_Q16divmod
DS50001456J-page 236
Description:
This function returns the quotient and remainder of its arguments.
Include:
<libq.h>
Prototype:
_Q16 _Q16mpy(_Q16 dividend, _Q16 divisor, _Q16
*remainder);
Argument:
dividend a fixed-point number in Q16 format. The value of this argument ranges from 0 to 2147483647.
divisor a fixed-point number in Q16 format. The value of this argument ranges from 0 to 2147483647.
remainder a pointer to an object large enough to hold the remainder.
This must be provided by the caller.
Return Value:
This function returns the quotient and remainder of its arguments.
The values range from 0 to 2147483647.
 2004-2014 Microchip Technology Inc.
Fixed-Point Math Functions
_Q16exp
Description:
This function finds the exponential value of a Q16 value.
Include:
<libq.h>
Prototype:
_Q16 _Q16exp(_Q16 x);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from -772244 to 681391.
Return Value:
This function returns the exponent value of x in Q16 format. The value
ranges from 0 to 2147483647.
_Q16log
Description:
This function finds the natural log of a Q16 value.
Include:
<libq.h>
Prototype:
_Q16 _Q16log(_Q16 x);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from 1 to 2147483647.
Return Value:
This function returns the natural log of x in Q16 format. The value
ranges from -726817 to 681391.
_Q16log10
Description:
This function finds the log (base 10) of a Q16 value.
Include:
<libq.h>
Prototype:
_Q16 _Q16log10(_Q16 x);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from 1 to 2147483647.
Return Value:
This function returns the log of x in Q16 format. The value ranges from
-315653 to 295925.
_Q16mac
Description:
This function multiplies the two 32-bit inputs, x and y, and accumulates
the product with prod. The function takes care of saturating the result
in case of underflow or overflow.
Include:
<libq.h>
Prototype:
_Q16 _Q16mac(_Q16x, _Q16 y, _Q16 prod);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from 0 to 2147483647.
y a fixed-point number in Q16 format. The value of this argument
ranges from 0 to 2147483647.
prod a fixed-point number in Q16 format. The value of this argument
ranges from 0 to 2147483647.
Return Value:
This function returns the multiplied and accumulated value prod in
Q16 format. The value ranges from 0 to 2147483647.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 237
16-Bit Language Tools Libraries
_Q16macNoSat
Description:
This function multiplies the two 32 bit inputs, x and y and accumulates
the product with prod.This function only sets the _Q16macSatFlag
variable in case of an overflow or underflow and does not take care of
saturation.
Include:
<libq.h>
Prototype:
_Q16 _Q16macNoSat(_Q16 x, _Q16 y, _Q16 prod);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from 0 to 2147483647.
y a fixed-point number in Q16 format. The value of this argument
ranges from 0 to 2147483647.
prod a fixed-point number in Q16 format. The value of this argument
ranges from 0 to 2147483647.
Return Value:
This function returns the multiplied and accumulated value prod in
Q16 format. The value ranges from 0 to 2147483647.
_Q16mpy
Description:
This function returns the product of its arguments.
Include:
<libq.h>
Prototype:
_Q16 _Q16mpy(_Q16 a,_Q16 b);
Argument:
a a fixed-point number in Q16 format. The value of this argument
ranges from 0 to 2147483647.
b a fixed-point number in Q16 format. The value of this argument
ranges from 0 to 2147483647.
Return Value:
This function returns the product of its arguments. The value ranges
from 0 to 2147483647.
_Q16neg
Description:
This function negates x with saturation. The value is saturated in the
case where the input is -2147483648.
Include:
<libq.h>
Prototype:
_Q16 _Q16neg(_Q16 x);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from -2147483648 to 2147483647.
Return Value:
This function returns the negated value of x in Q16 format. The value
ranges from -2147483648 to 2147483647.
_Q16norm
DS50001456J-page 238
Description:
This function finds the normalized value of a Q16 value.
Include:
<libq.h>
Prototype:
_Q16 _Q16norm(_Q16 x);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from -2147483648 to 2147483647.
Return Value:
This function returns the square root value of x in Q16 format. The
value ranges from 1073741824 to 2147483647 for a positive number
and -2147483648 to -1073741824 for a negative number.
 2004-2014 Microchip Technology Inc.
Fixed-Point Math Functions
_Q16power
Description:
This function finds the power result, given the base value, x, and the
power value, y.
Include:
<libq.h>
Prototype:
_Q16 _Q16power(_Q16 x, _Q16 y);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from 0 to 2147483647.
y a fixed-point number in Q16 format. The value of this argument
ranges from 0 to 2147483647.
Return Value:
This function returns the value of x to the power of y in Q16 format. The
value ranges from 0 to 2147483647.
_Q16random
Description:
This function generates a pseudo random number with a period of
2147483648. The function uses the _Q16randomSeed variable as a
random seed value.
Include:
<libq.h>
Prototype:
_Q16 _Q16random(void);
Argument:
None.
Return Value:
This function returns the generated random number in Q16 format. The
value of this output ranges from -2147483648 to 2147483647.
Remarks:
RndNum(n) = (RndNum(n-1) * RAN_MULT) + RAN_INC
SEED VALUE = 21845, RAN_MULT = 1664525 and
RAN_INC = 1013904223.
_Q16reciprocal
Description:
This function returns the reciprocal of a Q16 value.
Include:
<libq.h>
Prototype:
_Q16 _Q16reciprocal(_Q16 x);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from -2147483648 to 2147483647.
Return Value:
This function returns the reciprocal of x in Q16 format. The value of this
output ranges from -2147483648 to 2147483647.
_Q16reciprocalQ15
Description:
This function returns the reciprocal of a Q15 value. Since the input
range lies in the -1 to +1 region, the output is always greater than the -1
or +1 region. So, Q16 format is used to represent the output.
Include:
<libq.h>
Prototype:
_Q16 _Q16reciprocalQ15(_Q15 x);
Argument:
x a fixed-point number in Q15 format, which ranges from -215 to
215-1. The value of this argument ranges from -32768 to 32767.
Return Value:
This function returns the reciprocal of x in Q16 format. The value
ranges from -2147483648 to 2147418112.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 239
16-Bit Language Tools Libraries
_Q16reciprocalQ16
Description:
This function returns the reciprocal value of the input.
Include:
<libq.h>
Prototype:
_Q16 _Q16reciprocalQ16(_Q16 x);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from -2147483648 to 2147483647.
Return Value:
This function returns the reciprocal of x in Q16 format. The value of this
output ranges from -2147483648 to 2147483647.
_Q16shl
Description:
This function shifts the input argument, x, by y number of bits, to the
left if y is positive or to the right if y is negative. The function takes care
of saturating the result, in case of underflow or overflow.
Include:
<libq.h>
Prototype:
_Q16 _Q16shl(_Q16 x, short y);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from -2147483648 to 2147483647.
y an integer number, which ranges from -32 to +32.
Return Value:
This function returns the shifted value of x in Q16 format. The value
ranges from -2147483648 to 2147483647.
_Q16shlNoSat
Description:
This function shifts the input argument, x, by y number of bits, to the
left if y is positive or to the right if y is negative. The function sets the
_Q16shlSatFlag variable in case of underflow or overflow, but does
not take care of saturation.
Include:
<libq.h>
Prototype:
_Q16 _Q16shlNoSat(_Q16 x, short y);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from -2147483648 to 2147483647.
y an integer number, which ranges from -32 to +32.
Return Value:
This function returns the shifted value of x in Q16 format. The value
ranges from -2147483648 to 2147483647.
_Q16shr
DS50001456J-page 240
Description:
This function shifts the input argument, x, by y number of bits, to the
right if y is positive or to the left if y is negative. The function takes care
of saturating the result, in case of underflow or overflow.
Include:
<libq.h>
Prototype:
_Q16 _Q16shr(_Q16 x, short y);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from-2147483648 to 2147483647.
y an integer number, which ranges from -32 to +32.
Return Value:
This function returns the shifted value of x in Q16 format. The value
ranges from -2147483648 to 2147483647.
 2004-2014 Microchip Technology Inc.
Fixed-Point Math Functions
_Q16shrNoSat
Description:
This function shifts the input argument, x, by y number of bits, to the
right if y is positive or to the left if y is negative. The function sets the
_Q16shrSatFlag variable in case of underflow or overflow, but does
not take care of saturation.
Include:
<libq.h>
Prototype:
_Q16 _Q16shrNoSat(_Q16 x, short y);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from -2147483648 to 2147483647.
y an integer number, which ranges from -32 to +32.
Return Value:
This function returns the shifted value of x in Q16 format. The value
ranges from -2147483648 to 2147483647.
_Q16sin
Description:
This function finds the sine of a Q16 value.
Include:
<libq.h>
Prototype:
_Q16 _Q16sin(_Q16 x);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from -2147483648 to 2147483647.
Return Value:
This function returns the sine of x in Q16 format. The value ranges from
-65566 to 65536.
_Q16sinPI
Description:
This function finds the sine of PI () times a Q16 value.
Include:
<libq.h>
Prototype:
_Q16 _Q16sinPI(_Q16 x);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from -2147483648 to 2147483647.
Return Value:
This function returns the sine of PI times x in Q16 format. The value
ranges from -65536 to 65536.
_Q16sinSeries
Description:
Generates the sine series with the given normalizing frequency, f, and
the given number of samples, num, starting from start. Stores the
result in buffer, buf.
Include:
<libq.h>
Prototype:
short _Q16sinSeries(_Q16 f, short start, short num,
_Q16 *buf);
 2004-2014 Microchip Technology Inc.
DS50001456J-page 241
16-Bit Language Tools Libraries
_Q16sinSeries (Continued)
Argument:
f
a fixed-point number in Q16 format, which ranges from 0 to
(231-1). The valid range of values for this argument is from -32768 to
32768. This argument represents the Normalizing frequency.
start a fixed-point number in Q16 format, which ranges from 0 to
(231-1). The valid range of values for this argument is from 1 to 32767.
This argument represents the Starting Sample number in the Sine
Series.
num
a fixed-point number in Q16 format, which ranges from 0 to
(231-1). The valid range of values for this argument is from 1 to 32767.
This argument represents the Number of Sine Samples the function is
called to generate.
Note: num should not be more than 16383 for dsPIC and 32767 for PIC
devices.
buf
a pointer to the buffer where the generated sine samples would
get copied into.
Return Value:
This function returns num, the number of generated sine samples.
_Q16tan
Description:
This function finds the tangent of a Q16 value.
Include:
<libq.h>
Prototype:
_Q16 _Q16tan(_Q16 x);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from -2147483648 to 2147483647.
Return Value:
This function returns the tangent of x in Q16 format. The value ranges
from-2147483648 to 2147483647.
_Q16tanPI
DS50001456J-page 242
Description:
This function finds the tangent of PI () times a Q16 value.
Include:
<libq.h>
Prototype:
_Q16 _Q16tanPI(_Q16 x);
Argument:
x a fixed-point number in Q16 format. The value of this argument
ranges from -2147483648 to 2147483647.
Return Value:
This function returns the tangent of PI times x in Q16 format. The value
ranges from -2147483648 to 2147483647.
 2004-2014 Microchip Technology Inc.
Fixed-Point Math Functions
_Q16ftoi
Description:
This function converts a float value to a Q16 fixed-point fractional
value.
Include:
<libq.h>
Prototype:
_Q16 _Q16ftoi(float f);
Argument:
f a floating-point number. The value of this argument ranges from
-32768 to 32768.
Return Value:
This function returns a Q16 fixed-point fractional value. The value
ranges from -2147483648 to 2147483647.
_itofQ16
Description:
This function converts a Q16 fixed-point fractional value to a float
value.
Include:
<libq.h>
Prototype:
float _Q16ftoi(_Q16 q);
Argument:
q a fixed-point number. The value of this argument ranges from
-2147483648 to 2147483647.
Return Value:
This function returns a floating-point value. The value ranges from
-32768 to 32768.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 243
16-Bit Language Tools Libraries
NOTES:
DS50001456J-page 244
 2004-2014 Microchip Technology Inc.
16-BIT LANGUAGE TOOLS
LIBRARIES
Appendix A. ASCII Character Set
This table shows the ASCII character set in nibbles.
Most Significant Nibbles
Hex
Least
Significant
Nibbles
 2004-2014 Microchip Technology Inc.
0
1
2
3
4
5
6
7
0
NUL
DLE
Space
0
@
P
`
p
1
SOH
DC1
!
1
A
Q
a
q
2
STX
DC2
"
2
B
R
b
r
3
ETX
DC3
#
3
C
S
c
s
4
EOT
DC4
$
4
D
T
d
t
5
ENQ
NAK
%
5
E
U
e
u
6
ACK
SYN
&
6
F
V
f
v
7
Bell
ETB
'
7
G
W
g
w
8
BS
CAN
(
8
H
X
h
x
9
HT
EM
)
9
I
Y
i
y
A
LF
SUB
*
:
J
Z
j
z
B
VT
ESC
+
;
K
[
k
{
C
FF
FS
,
<
L
\
l
|
D
CR
GS
–
=
M
]
m
}
E
SO
RS
.
>
N
^
n
~
F
SI
US
/
?
O
_
o
DEL
DS50001456J-page 245
16-Bit Language Tools Libraries
NOTES:
DS50001456J-page 246
 2004-2014 Microchip Technology Inc.
16-BIT LANGUAGE TOOLS
LIBRARIES
Appendix B. Document Revision History
Revision J (December 2014)
• Section 2.14 “<stdlib.h> utility functions” - updated malloc function.
• Section 4.7 “Functions for Erasing and Writing Flash Memory” - updated
descriptions for _erase_flash (PIC24FXXKA Only) and
_write_flash_word24().
• Section 4.8 “Functions for Specialized Copying and Initialization” - the
following function descriptions have been updated:
- _memcpy_p2d24
- _memcpy_p2d16
- _strncpy_p2d24
- _strncpy_p2d16
Revision H
• Section 1.1 “Introduction” - added Compiler Installation Locations
• Section 2.10 “<signal.h> signal handling” - updated signal function.
• Section 2.13 “<stdio.h> input and output” - updated Customizing STDIO handles and descriptions for fdopen and vasprintf.
• Section 4.3 “Standard C Library Helper Functions” - updated
_dump_heap_info function.
• Section 4.7 “Functions for Erasing and Writing Flash Memory” - updated
descriptions for _write_flash_word32 and _write_flash_word48.
• Section 5.2 “Overview of Fixed-Point Data Formats” - inserted Table 5-1 and
Table 5-2.
• Section 5.4 “<libq.h> mathematical functions” - the following function descriptions have been updated:
- _Q16div
- _Q16divmod
- _Q16mpy
• Minor typographical changes.
Revision G
•
•
•
•
Section 2.13 “<stdio.h> input and output” - updated scanf function
Section 2.15 “<string.h> string functions” - updated memchr function
Inserted Section 5.2 “Overview of Fixed-Point Data Formats”
Minor typographical changes.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 247
MPLAB® XC16 C Compiler User’s Guide
Revision F
• Section 4.5 “Functions/Constants to Support A Simulated UART” - the following function descriptions have been updated:
- _delay_ms
- _delay_us
- _C30UART
• Section 4.6 “Functions for Erasing and Writing EEDATA Memory”- updated
_write_eedata_row function.
• Section 4.7 “Functions for Erasing and Writing Flash Memory” - updated
descriptions for _erase_flash and _write_flash_word24.
• Section 5.3 “Using the Fixed-Point Libraries” - updated descriptions for
Q16ftoi and itofQ16.
• Minor typographical changes.
Revision E
• Section 2.4 “<ctype.h> character handling” - the following function descriptions have been updated:
- islower
- isxdigit
- tolower
- toupper
• Section 2.6 “<float.h> floating-point characteristics”- the following function
descriptions have been updated:
- FLT_MAX_EXP
- FLT_MIN
- FLT_MIN_EXP
- LDBL_MIN
- LDBL_MIN_EXP
- UCHAR_MAX
- UINT_MAX
- ULLONG_MAX
- ULONG_MAX
- USHRT_MAX
• Section 2.9 “<setjmp.h> non-local jumps” - the following function descriptions
have been updated:
- jmp_buf
- longjmp
- SIGILL
- SIGSEGV
- raise
- signal
• Divided Chapter 3. “Standard C Libraries - Math Functions” into Chapter
4. “Standard C Libraries - Support Functions” and Chapter 5. “Fixed-Point
Math Functions”
• Minor typographical changes.
DS50001456J-page 248
 2004-2014 Microchip Technology Inc.
Document Revision History
Revision D
• Section 3.7 “<limits.h> implementation-defined limits” - the following function
descriptions have been updated:
- LLONG_MIN
- LONG_MAX
- LONG_MIN
- MB_LEN_MAX
- SCHAR_MAX
- SCHAR_MIN
- SHRT_MAX
- SHRT_MIN
- UCHAR_MAX
• Section 3.9 “<setjmp.h> non-local jumps” - the following function descriptions
have been updated:
- jmp_buf
- setjmp
- longjmp
• Section 3.10 “<signal.h> signal handling” - the following function descriptions
have been updated:
- SIGFPE
- SIGILL
- SIGINT
- raise
• Section 3.13 “<stdio.h> input and output”- the following function descriptions
have been updated:
- FILE
- fpos_t
- _IOFBF
- _IOLBF
- _IONBF
- BUFSIZ
- FOPEN_MAX
- L_tmpnam
- SEEK_CUR
- stderr
- stdout
- TMP_MAX
- clearerr
- feof
- fgetpos
- fopen
- fprintf
- fread
• Minor typographical changes
 2004-2014 Microchip Technology Inc.
DS50001456J-page 249
MPLAB® XC16 C Compiler User’s Guide
Revision C
• Updated Section 2.8 “<locale.h> localization” and the following function
descriptions:
- PIDInit
- PIDCoeffCalc
- PID
• Updated Section 2.9 “<setjmp.h> non-local jumps” and the following function
descriptions:
- Fract2Float
- Float2Fract
• Updated Section 3.2 “Using the Standard C Libraries”
• Section 3.3 “<math.h> mathematical functions” - the following function
descriptions have been updated:
- OpenXLCD
- putsXLCD
- SetDDRamAddr
- WriteDataXLCDWriteCmdXLCD
• Divided Section 3.3 “<math.h> mathematical functions” into Section 3.4
“CAN Functions”. The following function descriptions have been updated:
- CAN1AbortAll
- CAN1GetRXErrorCount
- CAN1GetTXErrorCount
- CAN1IsBusOff
- CAN1IsRXReady
- CAN1IsRXPassive
- CAN1IsTXPassive
• Section 5.2 “Overview of Fixed-Point Data Formats” - the following function
descriptions have been updated:
- _builtin_addab
- _builtin_add
- _builtin_btg
- _builtin_clr
- _builtin_clr_prefetch
- _builtin_dmaoffset
- _builtin_ed
- _builtin_edac
- _builtin_fbcl
- _builtin_mac
- _builtin_movsac
- _builtin_mpy
- _builtin_mpyn
- _builtin_msc
- _builtin_mulss
- _builtin_mulsu
- _builtin_mulus
- _builtin_muluu
- _builtin_nop
- _builtin_psvpage
• Minor typographical changes
DS50001456J-page 250
 2004-2014 Microchip Technology Inc.
Document Revision History
Revision B
• Added "NOTICE TO CUSTOMERS"
• Divided Chapter 4. “Standard C Libraries - Support Functions” into Chapter
5. “Fixed-Point Math Functions”
• Added Section 1.2 “OMF-Specific Libraries/Start-up Modules”
• Minor typographical changes
Revision A
• Initial release of this document.
 2004-2014 Microchip Technology Inc.
DS50001456J-page 251
16-BIT LANGUAGE TOOLS
LIBRARIES
Index
Symbols
^, Caret..................................................................... 86
__attach_input_file ................................................. 205
__C30_UART......................................................... 206
__close_input_file .................................................. 205
__delay_ms............................................................ 206
__delay_us............................................................. 206
__delay32 .............................................................. 206
__FILE__ ................................................................. 17
__LINE__ ................................................................. 17
_dump_heap_info .................................................. 199
_erase_eedata ....................................................... 208
_erase_eedata_all ................................................. 208
_erase_flash .......................................................... 211
_exit ....................................................................... 199
_init_prog_address ................................................ 217
_IOFBF .........................................................50, 87, 88
_IOLBF................................................................50, 88
_IONBF .........................................................50, 87, 88
_itoaQ15 ................................................................ 229
_itofQ15 ................................................................. 229
_itofQ16 ................................................................. 243
_MathError ............................................................... 41
_memcpy_p2d16 ................................................... 216
_memcpy_p2d24 ................................................... 216
_NSETJMP .............................................................. 36
_Q15abs ................................................................ 225
_Q15acos............................................................... 225
_Q15acosByPI ....................................................... 225
_Q15add ................................................................ 226
_Q15asin................................................................ 226
_Q15asinByPI ........................................................ 226
_Q15atan ............................................................... 226
_Q15atanByPI........................................................ 227
_Q15atanYByX ...................................................... 227
_Q15atanYByXByPI............................................... 227
_Q15atoi ................................................................ 227
_Q15cos................................................................. 228
_Q15cosPI ............................................................. 228
_Q15exp ................................................................ 228
_Q15ftoi ................................................................. 228
_Q15log ................................................................. 229
_Q15log10 ............................................................. 229
_Q15neg ................................................................ 230
_Q15norm .............................................................. 230
_Q15power ............................................................ 230
_Q15random .......................................................... 230
_Q15shl.................................................................. 231
_Q15shlNoSat........................................................ 231
_Q15shr ................................................................. 231
_Q15shrNoSat ....................................................... 231
DS50001456J-page 252
_Q15sin.................................................................. 232
_Q15sinPI .............................................................. 232
_Q15sinSeries........................................................ 232
_Q15sqrt ................................................................ 233
_Q15sub................................................................. 233
_Q15tan ................................................................. 233
_Q15tanPI .............................................................. 233
_Q16acos............................................................... 234
_Q16acosByPI ....................................................... 234
_Q16asin................................................................ 234
_Q16asinByPI ........................................................ 234
_Q16atan ............................................................... 235
_Q16atanByPI........................................................ 235
_Q16atanYByX ...................................................... 235
_Q16atanYByXByPI............................................... 235
_Q16cos................................................................. 236
_Q16cosPI ............................................................. 236
_Q16div.................................................................. 236
_Q16divmod........................................................... 236
_Q16exp................................................................. 237
_Q16ftoi.................................................................. 243
_Q16log.................................................................. 237
_Q16log10.............................................................. 237
_Q16mac (Continued)............................................ 237
_Q16macNoSat...................................................... 238
_Q16mpy................................................................ 238
_Q16neg ................................................................ 238
_Q16norm .............................................................. 238
_Q16power............................................................. 239
_Q16random .......................................................... 239
_Q16reciprocal....................................................... 239
_Q16reciprocalQ15 ................................................ 239
_Q16reciprocalQ16 ................................................ 240
_Q16shl.................................................................. 240
_Q16shlNoSat........................................................ 240
_Q16shr ................................................................. 240
_Q16shrNoSat ....................................................... 241
_Q16sin.................................................................. 241
_Q16sinPI .............................................................. 241
_Q16sinSeries........................................................ 241
_Q16tan ................................................................. 242
_Q16tanPI .............................................................. 242
_strncpy_p2d16...................................................... 216
_strncpy_p2d24...................................................... 217
_VERBOSE_DEBUGGING...................................... 17
_wait_eedata.......................................................... 209
_write_eedata_row................................................. 209
_write_eedata_word............................................... 209
_write_flash_word16 .............................................. 212
_write_flash_word24 .............................................. 212
_write_flash_word32 .............................................. 213
 2004-2014 Microchip Technology Inc.
Index
_write_flash_word48 .............................................. 213
_write_flash16 ........................................................ 211
_write_flash24 ........................................................ 212
-, Dash ..................................................................... 86
\f, Form Feed ........................................................... 23
\n, Newline .............................23, 47, 61, 66, 77, 78, 82
\r, Carriage Return ................................................... 23
\t, Horizontal Tab...................................................... 23
\v, Vertical Tab ......................................................... 23
#if ............................................................................. 33
#include............................................. 16, 153, 198, 223
%, Percent ............................................ 80, 85, 86, 151
Numerics
0x ........................................................ 24, 79, 119, 120
A
Abnormal Termination Signal................................... 38
abort ....................................................................17, 98
abs ........................................................................... 99
Absolute Value
Double Floating Point ..................................... 169
Integer............................................................... 99
Long Integer.................................................... 109
Single Floating Point ....................................... 169
Absolute Value Function
abs .................................................................... 99
fabs ................................................................. 169
fabsf ................................................................ 169
labs ................................................................. 109
Access Mode
Binary...........................................................55, 62
Text ..............................................................55, 62
acos ....................................................................... 155
acosf ...................................................................... 156
Allocate Memory .................................................... 111
calloc............................................................... 105
Free ................................................................ 108
realloc ............................................................. 115
Alphabetic Character
Defined ............................................................. 18
Test for.............................................................. 18
Alphanumeric Character
Defined ............................................................. 18
Test for.............................................................. 18
AM/PM ................................................................... 151
Append............................................................128, 134
arccosine
Double Floating Point ..................................... 155
Single Floating Point ....................................... 156
arcsine
Double Floating Point ..................................... 157
Single Floating Point ....................................... 157
arctangent
Double Floating Point ..................................... 158
Single Floating Point ....................................... 159
arctangent of y/x
Double Floating Point ..................................... 159
Single Floating Point ....................................... 161
Argument List .................................... 43, 93, 94, 95, 96
Arithmetic Error Message......................................... 38
 2004-2014 Microchip Technology Inc.
ASCII Character Set............................................... 245
asctime................................................................... 146
asin......................................................................... 157
asinf........................................................................ 157
assert ....................................................................... 17
assert.h .................................................................... 17
Assignment Suppression ......................................... 85
Asterisk .............................................................. 79, 85
atan ........................................................................ 158
atan2 ...................................................................... 159
atan2f ..................................................................... 161
atanf ....................................................................... 159
atexit................................................................. 99, 107
atof ......................................................................... 101
atoi ......................................................................... 102
atol ......................................................................... 102
attach_input_file ..................................................... 205
B
Base ............................................................... 119, 120
10 ..................................... 29, 30, 31, 32, 181, 182
2 ........................................................................ 31
e .............................................................. 180, 183
FLT_RADIX.......................... 28, 29, 30, 31, 32, 33
Binary
Base.................................................................. 31
Mode ......................................................55, 62, 90
Search............................................................. 103
Streams............................................................. 47
Bitfields..................................................................... 46
brk .................................................................. 200, 203
bsearch .................................................................. 103
Buffer Size.......................................................... 50, 88
Buffering Modes ....................................................... 88
Buffering, See File Buffering
BUFSIZ .............................................................. 50, 87
Built-in Functions...................................................... 13
C
C Locale ............................................................. 18, 35
C30_UART............................................................. 206
Calendar Time......................... 145, 147, 148, 150, 152
calloc .............................................................. 105, 108
Caret (^) ................................................................... 86
Carriage Return........................................................ 23
ceil.......................................................................... 162
ceilf......................................................................... 163
ceiling
Double Floating Point...................................... 162
Single Floating Point ....................................... 163
char
Maximum Value ................................................ 33
Minimum Value ................................................. 33
Number of Bits .................................................. 33
CHAR_BIT ............................................................... 33
CHAR_MAX ............................................................. 33
CHAR_MIN .............................................................. 33
Character Array........................................................ 86
Character Case Mapping
Lower Case Alphabetic Character .................... 25
Upper Case Alphabetic Character .................... 26
DS50001456J-page 253
16-Bit Language Tools Libraries
Character Case Mapping Functions
tolower .............................................................. 25
toupper .............................................................. 26
Character Handling, See ctype.h
Character Input/Output Functions
fgetc .................................................................. 59
fgets .................................................................. 61
fputc .................................................................. 65
fputs .................................................................. 65
getc ................................................................... 76
getchar .............................................................. 77
gets ................................................................... 77
putc ................................................................... 81
putchar .............................................................. 82
puts ................................................................... 82
ungetc ............................................................... 91
Character Testing
Alphabetic Character ........................................ 18
Alphanumeric Character ................................... 18
Control Character.............................................. 19
Decimal Digit ..................................................... 20
Graphical Character .......................................... 20
Hexadecimal Digit ............................................. 24
Lower Case Alphabetic Character .................... 21
Printable Character ........................................... 22
Punctuation Character ...................................... 22
Upper Case Alphabetic Character .................... 24
White-Space Character..................................... 23
Character Testing Functions
isalnum.............................................................. 18
isalpha............................................................... 18
iscntrl................................................................. 19
isdigit ................................................................. 20
isgraph .............................................................. 20
islower ............................................................... 21
isprint ................................................................ 22
ispunct............................................................... 22
isspace .............................................................. 23
isupper .............................................................. 24
isxdigit ............................................................... 24
Characters
Alphabetic ......................................................... 18
Alphanumeric .................................................... 18
Control .............................................................. 19
Convert to Lower Case Alphabetic.................... 25
Convert to Upper Case Alphabetic.................... 26
Decimal Digit ..................................................... 20
Graphical........................................................... 20
Hexadecimal Digit ............................................. 24
Lower Case Alphabetic ..................................... 21
Printable ............................................................ 22
Punctuation ....................................................... 22
Upper Case Alphabetic ..................................... 24
White-Space ..................................................... 23
Classifying Characters ............................................. 18
clearerr ..................................................................... 53
Clearing Error Indicator ............................................ 53
clock ....................................................................... 146
clock_t ............................................................ 145, 146
CLOCKS_PER_SEC.............................................. 145
DS50001456J-page 254
close ....................................................................... 201
close_input_file....................................................... 205
COFF........................................................................ 12
Common Definitions, See stddef.h
Compare Strings .................................................... 130
Comparison Function ..................................... 103, 114
Comparison Functions
memcmp ......................................................... 123
strcmp ............................................................. 130
strcoll............................................................... 131
strncmp ........................................................... 136
strxfrm ............................................................. 144
Compiler Options
-fno-short-double............................................... 48
-msmart-io ......................................................... 47
Concatenation Functions
strcat ............................................................... 128
strncat ............................................................. 134
Control Character
Defined.............................................................. 19
Test for .............................................................. 19
Control Transfers...................................................... 36
Conversion ................................................... 79, 85, 89
Convert
Character to Multibyte Character .................... 121
Multibyte Character to Wide Character ........... 113
Multibyte String to Wide Character String ....... 113
String to Double Floating Point ............... 101, 118
String to Integer............................................... 102
String to Long Integer.............................. 102, 119
String to Unsigned Long Integer ..................... 120
To Lower Case Alphabetic Character ............... 25
To Upper Case Alphabetic Character ............... 26
Wide Character String to Multibyte String ....... 121
Copying Functions
memcpy........................................................... 125
memmove ....................................................... 126
memset ........................................................... 127
strcpy............................................................... 131
strncpy............................................................. 137
cos.......................................................................... 163
cosf......................................................................... 164
cosh........................................................................ 165
coshf....................................................................... 166
cosine
Double Floating Point...................................... 163
Single Floating Point ....................................... 164
crt0, crt1 ................................................................... 12
ctime....................................................................... 147
ctype.h...................................................................... 18
isalnum .............................................................. 18
iscntrl................................................................. 19
isdigit ................................................................. 20
isgraph .............................................................. 20
islapha............................................................... 18
islower ............................................................... 21
ispring................................................................ 22
ispunct............................................................... 22
isspace .............................................................. 23
isupper .............................................................. 24
 2004-2014 Microchip Technology Inc.
Index
isxdigit ............................................................... 24
tolower .............................................................. 25
toupper.............................................................. 26
Current Argument .................................................... 43
Customer Notification Service.................................... 8
Customer Support ...................................................... 9
Customized Function ............................................. 108
D
Dash (-) .................................................................... 86
Date and Time ....................................................... 150
Date and Time Functions, See time.h
Day of the Month.....................................145, 146, 150
Day of the Week .....................................145, 146, 150
Day of the Year ...............................................145, 151
Daylight Savings Time ............................145, 148, 149
DBL_DIG.................................................................. 28
DBL_EPSILON ........................................................ 28
DBL_MANT_DIG ..................................................... 28
DBL_MAX ................................................................ 28
DBL_MAX_10_EXP ................................................. 29
DBL_MAX_EXP ....................................................... 29
DBL_MIN ................................................................. 29
DBL_MIN_10_EXP .................................................. 29
DBL_MIN_EXP ........................................................ 30
Deallocate Memory .........................................108, 115
Debugging Logic Errors ........................................... 17
Decimal ............................................... 80, 86, 119, 120
Decimal Digit
Defined ............................................................. 20
Number Of .............................................28, 30, 31
Test for.............................................................. 20
Decimal Point ........................................................... 79
Default Handler ........................................................ 37
delay_ms................................................................ 206
delay_us................................................................. 206
delay32 .................................................................. 206
Diagnostics, See assert.h
difftime ................................................................... 148
Digit, Decimal, See Decimal Digit
Digit, Hexadecimal, See Hexadecimal Digit
Direct Input/Output Functions
fread.................................................................. 66
fwrite ................................................................. 74
div .....................................................................97, 105
div_t ......................................................................... 97
Divide
Integer............................................................. 105
Long Integer.................................................... 110
Divide by Zero .............................................38, 41, 105
Documentation
Conventions ........................................................ 6
Layout ................................................................. 5
Domain Error..... 27, 155, 156, 157, 159, 161, 163, 164,
171, 173, 180, 181, 182, 183, 188, 189, 192, 193, 194
dot ............................................................................ 79
Double Precision Floating Point
Machine Epsilon ............................................... 28
Maximum Exponent (base 10) .......................... 29
Maximum Exponent (base 2) ............................ 29
Maximum Value ................................................ 28
 2004-2014 Microchip Technology Inc.
Minimum Exponent (base 10) ........................... 29
Minimum Exponent (base 2) ............................. 30
Minimum Value ................................................. 29
Number of Binary Digits .................................... 28
Number of Decimal Digits ................................. 28
double Type ............................................................. 48
Dream Function........................................................ 79
dump heap info ...................................................... 199
Duplicate a string ................................................... 117
DWARF .................................................................... 12
E
EDOM ...................................................................... 27
edom ...................................................................... 155
ELF........................................................................... 12
Ellipses (...) ........................................................ 43, 86
Empty Binary File ............................................... 55, 62
Empty Text File .................................................. 55, 62
End Of File ............................................................... 50
Indicator ............................................................ 47
Seek.................................................................. 70
Test For............................................................. 57
Environment Function
getenv ............................................................. 108
Environment Variable............................................. 204
EOF.......................................................................... 50
ERANGE .................................................................. 27
erange .................................................................... 155
erase_eedata ......................................................... 208
erase_eedata_all.................................................... 208
erase_flash............................................................. 211
errno................................................................. 27, 155
errno.h.......................................................27, 155, 202
EDOM ............................................................... 27
ERANGE........................................................... 27
errno.................................................................. 27
Error Codes...................................................... 27, 133
Error Conditions ..................................................... 155
Error Handler.......................................................... 105
Error Handling Functions
clearerr.............................................................. 53
feof .................................................................... 57
ferror ................................................................. 58
perror ................................................................ 78
Error Indicator .......................................................... 47
Error Indicators
Clearing....................................................... 53, 84
End Of File .................................................. 53, 61
Error ............................................................ 53, 61
Test For............................................................. 58
Error Signal .............................................................. 37
Errors, See errno.h
Errors, Testing For ................................................... 27
Exception Error ...................................................... 105
exit................................................. 90, 97, 99, 107, 199
EXIT_FAILURE ........................................................ 97
EXIT_SUCCESS...................................................... 97
exp ......................................................................... 167
expf ........................................................................ 168
Exponential and Logarithmic Functions
exp .................................................................. 167
DS50001456J-page 255
16-Bit Language Tools Libraries
expf ................................................................. 168
frexp ................................................................ 175
frexpf ............................................................... 176
ldexp ............................................................... 177
ldexpf .............................................................. 178
log ................................................................... 180
log10 ............................................................... 181
log10f .............................................................. 182
logf .................................................................. 183
modf ................................................................ 184
modff ............................................................... 185
Exponential Function
Double Floating Point...................................... 167
Single Floating Point ....................................... 168
F
fabs ........................................................................ 169
fabsf ....................................................................... 169
fclose ................................................................ 54, 201
fdopen ...................................................................... 55
feof ..................................................................... 53, 57
ferror................................................................... 53, 58
fflush................................................................. 59, 203
fgetc ................................................................. 59, 202
fgetpos ............................................................. 60, 201
fgets ................................................................. 61, 202
Field Width ............................................................... 79
FILE...............................................................17, 47, 50
File Access Functions
fclose................................................................. 54
fdopen ............................................................... 55
fflush ................................................................. 59
fopen ................................................................. 62
freopen .............................................................. 68
setbuf ................................................................ 87
setvbuf .............................................................. 88
File Access Modes ........................................47, 55, 62
File Buffering
Fully Buffered .............................................. 47, 50
Line Buffered............................................... 47, 50
Unbuffered .................................................. 47, 50
File Operations
Remove............................................................. 83
Rename ............................................................ 83
File Positioning Functions
fgetpos .............................................................. 60
fseek ................................................................. 70
fsetpos .............................................................. 71
ftell .................................................................... 73
rewind ............................................................... 84
FILENAME_MAX...................................................... 51
File-Position Indicator.......47, 50, 59, 60, 65, 66, 71, 74
Files, Maximum Number Open................................. 51
Fixed Point Math Library ........................................ 219
flags.......................................................................... 79
float.h ....................................................................... 28
DBL_DIG........................................................... 28
DBL_EPSILON ................................................. 28
DBL_MANT_DIG .............................................. 28
DBL_MAX ......................................................... 28
DBL_MAX_10_EXP .......................................... 29
DS50001456J-page 256
DBL_MAX_EXP ................................................ 29
DBL_MIN........................................................... 29
DBL_MIN_10_EXP ........................................... 29
DBL_MIN_EXP ................................................. 30
FLT_DIG ........................................................... 30
FLT_EPSILON .................................................. 30
FLT_MANT_DIG ............................................... 30
FLT_MAX .......................................................... 30
FLT_MAX_10_EXP........................................... 30
FLT_MAX_EXP................................................. 31
FLT_MIN ........................................................... 31
FLT_MIN_10_EXP ............................................ 31
FLT_MIN_EXP .................................................. 31
FLT_RADIX....................................................... 31
FLT_ROUNDS .................................................. 31
LDBL_DIG......................................................... 31
LDBL_EPSILON................................................ 32
LDBL_MANT_DIG............................................. 32
LDBL_MAX ....................................................... 32
LDBL_MAX_10_EXP ........................................ 32
LDBL_MAX_EXP .............................................. 32
LDBL_MIN......................................................... 32
LDBL_MIN_10_EXP ......................................... 32
LDBL_MIN_EXP ............................................... 33
Floating Point
Limits................................................................. 28
No Conversion .................................................. 47
Types, Properties Of ......................................... 28
Floating Point, See float.h
Floating-Point Error Signal ....................................... 38
floor ........................................................................ 170
Double Floating Point...................................... 170
Single Floating Point ....................................... 170
floorf ....................................................................... 170
FLT_DIG................................................................... 30
FLT_EPSILON ......................................................... 30
FLT_MANT_DIG ...................................................... 30
FLT_MAX ................................................................. 30
FLT_MAX_10_EXP .................................................. 30
FLT_MAX_EXP ........................................................ 31
FLT_MIN .................................................................. 31
FLT_MIN_10_EXP ................................................... 31
FLT_MIN_EXP ......................................................... 31
FLT_RADIX .............................................................. 31
FLT_RADIX Digit
Number Of............................................. 28, 30, 32
FLT_ROUNDS ......................................................... 31
Flush................................................................. 59, 107
fmod ....................................................................... 171
fmodf ...................................................................... 173
-fno-short-double .....................................28, 29, 30, 48
fopen .....................................................47, 62, 88, 202
FOPEN_MAX ........................................................... 51
Form Feed................................................................ 23
Format Specifiers ............................................... 79, 85
Formatted I/O Routines ............................................ 47
Formatted Input/Output Functions
fprintf ................................................................. 64
fscanf................................................................. 68
printf .................................................................. 79
 2004-2014 Microchip Technology Inc.
Index
scanf ................................................................. 85
sprintf ................................................................ 89
sscanf ............................................................... 89
vasprintf ............................................................ 93
vfprintf ............................................................... 94
vprintf ................................................................ 95
vsprintf .............................................................. 96
Formatted Text
Printing.............................................................. 89
Scanning ........................................................... 89
fpos_t ....................................................................... 50
fprintf ...................................................................47, 64
fputc ......................................................................... 65
fputs ......................................................................... 65
fraction and exponent function
Double Floating Point ..................................... 175
Single Floating Point ....................................... 176
Fraction Digits .......................................................... 79
fread ..................................................................66, 202
free ......................................................................... 108
Free Memory.......................................................... 108
freopen ........................................................47, 68, 202
frexp ....................................................................... 175
frexpf ...................................................................... 176
fscanf ..................................................................47, 68
fseek ...........................................................70, 91, 201
fsetpos ........................................................71, 91, 201
ftell ....................................................................73, 201
Full Buffering .......................................................87, 88
Fully Buffered ......................................................47, 50
fwrite ........................................................................ 74
G
getc .......................................................................... 76
getchar ..................................................................... 77
getenv .............................................................108, 204
gets ...................................................................77, 202
GMT ....................................................................... 148
gmtime ............................................................148, 149
Graphical Character
Defined ............................................................. 20
Test for.............................................................. 20
Greenwich Mean Time ........................................... 148
H
h modifier ............................................................80, 85
Handler
Default .............................................................. 37
Error ................................................................ 105
Interrupt ............................................................ 41
Nested .............................................................. 36
Signal ...........................................................37, 42
Signal Type....................................................... 37
Handling
Interrupt Signal ................................................. 42
Header Files
assert.h ............................................................. 17
ctype.h .............................................................. 18
errno.h ...............................................27, 155, 202
float.h ................................................................ 28
libq.h ............................................................... 225
 2004-2014 Microchip Technology Inc.
limits.h............................................................... 33
locale.h.............................................................. 35
math.h ............................................................. 155
setjmp.h ............................................................ 36
signal.h.............................................................. 37
stdarg.h ............................................................. 43
stddef.h ............................................................. 45
stdio.h ....................................................... 47, 204
stdlib.h....................................................... 97, 204
string.h ............................................................ 122
time.h ...................................................... 145, 205
Heap....................................................................... 200
Hexadecimal ....................................... 80, 86, 119, 120
Hexadecimal Conversion ......................................... 79
Hexadecimal Digit
Defined.............................................................. 24
Test for.............................................................. 24
Horizontal Tab.......................................................... 23
Hour ........................................................145, 146, 150
HUGE_VAL ............................................................ 155
Hyperbolic Cosine
Double Floating Point...................................... 165
Single Floating Point ....................................... 166
Hyperbolic Functions
cosh ................................................................ 165
coshf ............................................................... 166
sinh ................................................................. 190
sinhf ................................................................ 191
tanh ................................................................. 195
tanhf ................................................................ 196
Hyperbolic Sine
Double Floating Point...................................... 190
Single Floating Point ....................................... 191
Hyperbolic Tangent
Double Floating Point...................................... 195
hyperbolic tangent
Single Floating Point ....................................... 196
I
Ignore Signal ............................................................ 37
Illegal Instruction Signal ........................................... 39
Implementation-Defined Limits, See limits.h
Indicator
End Of File .................................................. 47, 50
Error ............................................................ 47, 58
File Position ....................47, 59, 60, 65, 66, 71, 74
Infinity..................................................................... 155
init_prog_address................................................... 217
Input and Output, See stdio.h
Input Formats ........................................................... 47
Instruction Cycles....................................148, 149, 152
int
Maximum Value ................................................ 33
Minimum Value ................................................. 33
INT_MAX.................................................................. 33
INT_MIN ................................................................... 33
Integer Limits............................................................ 33
Internal Error Message........................................... 133
Internet Address, Microchip ....................................... 8
Interrupt Handler ...................................................... 41
Interrupt Signal......................................................... 39
DS50001456J-page 257
16-Bit Language Tools Libraries
Interrupt Signal Handling.......................................... 42
Interruption Message ............................................... 39
Invalid Executable Code Message ........................... 39
Invalid Storage Request Message ........................... 40
Inverse Cosine, See arccosine
Inverse Sine, See arcsine
Inverse Tangent, See arctangent
IOFBF............................................................50, 87, 88
IOLBF ................................................................. 50, 88
IONBF ...........................................................50, 87, 88
isalnum ..................................................................... 18
iscntrl ........................................................................ 19
isdigit ........................................................................ 20
isgraph ..................................................................... 20
islapha ...................................................................... 18
islower ...................................................................... 21
isprint........................................................................ 22
ispunct ...................................................................... 22
isspace ..................................................................... 23
isupper ..................................................................... 24
isxdigit ...................................................................... 24
J
jmp_buf .................................................................... 36
Justify ....................................................................... 79
L
L modifier ........................................................... 80, 85
l modifier............................................................. 80, 85
L_tmpnam .......................................................... 51, 91
labs......................................................................... 109
LC_ALL .................................................................... 35
LC_COLLATE .......................................................... 35
LC_CTYPE............................................................... 35
LC_MONETARY ...................................................... 35
LC_NUMERIC .......................................................... 35
LC_TIME .................................................................. 35
lconv, struct .............................................................. 35
LDBL_DIG ................................................................ 31
LDBL_EPSILON....................................................... 32
LDBL_MANT_DIG.................................................... 32
LDBL_MAX .............................................................. 32
LDBL_MAX_10_EXP ............................................... 32
LDBL_MAX_EXP ..................................................... 32
LDBL_MIN................................................................ 32
LDBL_MIN_10_EXP ................................................ 32
LDBL_MIN_EXP ...................................................... 33
ldexp....................................................................... 177
ldexpf...................................................................... 178
ldiv .................................................................... 97, 110
ldiv_t ......................................................................... 97
Leap Second .................................................. 145, 151
Left Justify ................................................................ 79
libc ............................................................................ 13
libdsp ........................................................................ 12
libm........................................................................... 13
libp............................................................................ 12
libpic30 ..................................................................... 13
libpic30, Rebuilding ................................................ 198
libq.h....................................................................... 225
Libraries
DS50001456J-page 258
Fixed Point Math ............................................. 219
Math ................................................................ 153
Standard C ........................................................ 15
Standard C Math ............................................. 155
Support............................................................ 197
Limits
Floating Point .................................................... 28
Integer ............................................................... 33
limits.h ...................................................................... 33
CHAR_BITS ...................................................... 33
CHAR_MAX ...................................................... 33
CHAR_MIN ....................................................... 33
INT_MAX........................................................... 33
INT_MIN............................................................ 33
LLONG_MAX .................................................... 33
LLONG_MIN ..................................................... 34
LONG_MAX. ..................................................... 34
LONG_MIN. ...................................................... 34
MB_LEN_MAX. ................................................. 34
SCHAR_MAX.................................................... 34
SCHAR_MIN ..................................................... 34
SHRT_MAX....................................................... 34
SHRT_MIN........................................................ 34
UCHAR_MAX.................................................... 35
UINT_MAX. ....................................................... 35
ULLONG_MAX.................................................. 35
ULONG_MAX.................................................... 35
USHRT_MAX. ................................................... 35
LINE ......................................................................... 17
Line Buffered ...................................................... 47, 50
Line Buffering ........................................................... 88
ll modifier ............................................................ 80, 85
LLONG_MAX ........................................................... 33
LLONG_MIN............................................................. 34
Load Exponent Function
Double Floating Point...................................... 177
Single Floating Point ....................................... 178
Local Time.............................................. 147, 149, 150
Locale, C ............................................................ 18, 35
Locale, Other............................................................ 35
locale.h ..................................................................... 35
localeconv ................................................................ 35
Localization, See locale.h
localtime ................................................. 147, 148, 149
Locate Character.................................................... 129
log........................................................................... 180
log10....................................................................... 181
log10f...................................................................... 182
Logarithm Function
Double Floating Point...................................... 181
Single Floating Point ....................................... 182
Logarithm Function, Natural
Double Floating Point...................................... 180
Single Floating Point ....................................... 183
logf.......................................................................... 183
Logic Errors, Debugging........................................... 17
Long Double Precision Floating Point
Machine Epsilon................................................ 32
Maximum Exponent (base 10) .......................... 32
Maximum Exponent (base 2) ............................ 32
 2004-2014 Microchip Technology Inc.
Index
Maximum Value ................................................ 32
Minimum Exponent (base 10) ........................... 32
Minimum Exponent (base 2) ............................. 33
Minimum Value ................................................. 32
Number of Binary Digits .................................... 32
Number of Decimal Digits ................................. 31
long double Type ..................................................... 48
long int
Maximum Value ................................................ 34
Minimum Value ................................................. 34
long long int
Maximum Value ................................................ 33
Minimum Value ................................................. 34
long long unsigned int
Maximum Value ................................................ 35
long unsigned int
Maximum Value ................................................ 35
LONG_MAX ............................................................. 34
LONG_MIN .............................................................. 34
longjmp .................................................................... 36
Lower Case Alphabetic Character
Convert To ........................................................ 25
Defined ............................................................. 21
Test for.............................................................. 21
lseek....................................................................... 201
M
Machine Epsilon
Double Floating Point ....................................... 28
Long Double Floating Point .............................. 32
Single Floating Point ......................................... 30
Magnitude ................155, 167, 168, 171, 173, 190, 191
malloc.............................................. 108, 111, 200, 203
Mapping Characters................................................. 18
Math Exception Error ............................................. 105
Math Library ........................................................... 153
math.h .................................................................... 155
acos. ............................................................... 155
acosf. .............................................................. 156
asin. ................................................................ 157
asinf ................................................................ 157
atan................................................................. 158
atan2. .............................................................. 159
atan2f. ............................................................. 161
atanf. ............................................................... 159
ceil .................................................................. 162
ceilf ................................................................. 163
cos .................................................................. 163
cosf ................................................................. 164
cosh ................................................................ 165
coshf ............................................................... 166
exp .................................................................. 167
expf ................................................................. 168
fabs ................................................................. 169
fabsf ................................................................ 169
floor ................................................................. 170
floorf ................................................................ 170
fmod................................................................ 171
fmodf ............................................................... 173
frexp................................................................ 175
frexpf ............................................................... 176
 2004-2014 Microchip Technology Inc.
HUGE_VAL..................................................... 155
ldexp ............................................................... 177
ldexpf .............................................................. 178
log ................................................................... 180
log10 ............................................................... 181
log10f .............................................................. 182
logf .................................................................. 183
modf ................................................................ 184
modff ............................................................... 185
pow ................................................................. 186
powf ................................................................ 187
sin ................................................................... 188
sinf .................................................................. 189
sinh ................................................................. 190
sinhf ................................................................ 191
sqrt .................................................................. 192
sqrtf ................................................................. 193
tan ................................................................... 194
tanf .................................................................. 194
tanh ................................................................. 195
tanhf ................................................................ 196
Mathematical Functions, See libq.h
Mathematical Functions, See math.h
MathError ................................................................. 41
Maximum
Multibyte Character........................................... 98
Maximum Value
Double Floating-Point Exponent (base 10) ....... 29
Double Floating-Point Exponent (base 2) ......... 29
Long Double Floating-Point Exponent (base 10) ..
32
Long Double Floating-Point Exponent (base 2) 32
Multibyte Character........................................... 34
rand................................................................... 98
Single Floating-Point Exponent (base 10) ........ 30
Single Floating-Point Exponent (base 2) .......... 31
Type char .......................................................... 33
Type Double...................................................... 28
Type int ............................................................. 33
Type Long Double............................................. 32
Type long int ..................................................... 34
Type long long int.............................................. 33
Type long long unsigned int .............................. 35
Type long unsigned int...................................... 35
Type short int .................................................... 34
Type signed char .............................................. 34
Type Single ....................................................... 30
Type unsigned char .......................................... 35
Type unsigned int.............................................. 35
Type unsigned short int..................................... 35
MB_CUR_MAX ........................................................ 98
MB_LEN_MAX ......................................................... 34
mblen ..................................................................... 113
mbstowcs ............................................................... 113
mbtowc................................................................... 113
memchr .................................................................. 122
memcmp ................................................................ 123
memcpy.................................................................. 125
memcpy_p2d16...................................................... 216
memcpy_p2d24...................................................... 216
DS50001456J-page 259
16-Bit Language Tools Libraries
memmove .............................................................. 126
Memory
Allocate ....................................................105, 111
Deallocate ....................................................... 108
Free ................................................................ 108
Reallocate ....................................................... 115
memset .................................................................. 127
Message
Arithmetic Error ................................................. 38
Interrupt ............................................................ 39
Invalid Executable Code ................................... 39
Invalid Storage Request ................................... 40
Termination Request ........................................ 40
Minimum Value
Double Floating-Point Exponent (base 10) ....... 29
Double Floating-Point Exponent (base 2) ......... 30
Long Double Floating-Point Exponent (base 10) ..
32
Long Double Floating-Point Exponent (base 2) 33
Single Floating-Point Exponent (base 10) ........ 31
Single Floating-Point Exponent (base 2) .......... 31
Type char .......................................................... 33
Type Double ..................................................... 29
Type int ............................................................. 33
Type Long Double ............................................ 32
Type long int ..................................................... 34
Type long long int ............................................. 34
Type short int .................................................... 34
Type signed char .............................................. 34
Type Single....................................................... 31
Minute .....................................................145, 146, 151
mktime ................................................................... 150
modf ....................................................................... 184
modff ...................................................................... 185
modulus function
Double Floating Point ..................................... 184
Single Floating Point ....................................... 185
Month .............................................. 145, 146, 150, 151
-msmart-io ................................................................ 47
Multibyte Character ...................................98, 113, 121
Maximum Number of Bytes............................... 34
Multibyte String ...............................................113, 121
N
NaN ........................................................................ 155
Natural Logarithm
Double Floating Point ..................................... 180
Single Floating Point ....................................... 183
NDEBUG.................................................................. 17
Nearest Integer Functions
ceil .................................................................. 162
ceilf ................................................................. 163
floor ................................................................. 170
floorf ................................................................ 170
Nested Signal Handler ............................................. 36
Newline ..................................23, 47, 61, 66, 77, 78, 82
No Buffering ............................................ 47, 50, 87, 88
Non-Local Jumps, See setjmp.h
NSETJMP ................................................................ 36
NULL....................................... 35, 45, 51, 98, 122, 146
DS50001456J-page 260
O
Object Module Format.............................................. 12
Octal.................................................... 80, 86, 119, 120
Octal Conversion...................................................... 79
offsetof ..................................................................... 46
OMF ......................................................................... 12
open ....................................................................... 201
Output Formats ........................................................ 47
Overflow Errors ..27, 155, 167, 168, 177, 178, 186, 187
Overlap............................ 125, 126, 128, 131, 134, 137
P
Pad Characters ........................................................ 79
Percent.................................................. 80, 85, 86, 151
Peripheral Libraries .................................................. 12
perror........................................................................ 78
pic30-libs
__attach_input_file.......................................... 205
__C30_UART.................................................. 206
__close_input_file ........................................... 205
__delay_ms..................................................... 206
__delay_us...................................................... 206
__delay32 ....................................................... 206
_dump_heap_info ........................................... 199
_erase_eedata ................................................ 208
_erase_eedata_all .......................................... 208
_erase_flash ................................................... 211
_exit ................................................................ 199
_init_prog_address ......................................... 217
_memcpy_p2d16 ............................................ 216
_memcpy_p2d24 ............................................ 216
_strncpy_p2d16 .............................................. 216
_strncpy_p2d24 .............................................. 217
_wait_eedata................................................... 209
_write_eedata_row.......................................... 209
_write_eedata_word........................................ 209
_write_flash_word16 ....................................... 212
_write_flash_word24 ....................................... 212
_write_flash_word32 ....................................... 213
_write_flash_word48 ....................................... 213
_write_flash16................................................. 211
_write_flash24................................................. 212
brk ................................................................... 200
close................................................................ 201
getenv ............................................................. 204
lseek................................................................ 201
open ................................................................ 201
read................................................................. 202
remove ............................................................ 204
rename............................................................ 204
sbrk ................................................................. 202
system............................................................. 204
time ................................................................. 205
write ................................................................ 203
Plus Sign .................................................................. 79
Pointer, Temporary ................................................ 115
pow......................................................................... 186
Power Function
Double Floating Point...................................... 186
Single Floating Point ....................................... 187
Power Functions
 2004-2014 Microchip Technology Inc.
Index
pow ................................................................. 186
powf ................................................................ 187
powf ....................................................................... 187
precision................................................................... 79
Prefix ...................................................................24, 79
Print Formats ........................................................... 47
Printable Character
Defined ............................................................. 22
Test for.............................................................. 22
printf ....................................................................47, 79
Processor Clocks per Second................................ 145
Processor Time ...............................................145, 146
Pseudo-Random Number ...............................115, 117
ptrdiff_t ..................................................................... 45
Punctuation Character
Defined ............................................................. 22
Test for.............................................................. 22
Pushed Back ............................................................ 91
putc .......................................................................... 81
putchar ..................................................................... 82
puts .......................................................................... 82
Q
Q15 Functions........................................................ 225
Q16 Functions........................................................ 234
qsort ................................................................103, 114
Quick Sort .............................................................. 114
R
Radix ........................................................................ 31
raise ............................................ 37, 38, 39, 40, 41, 42
rand .................................................................115, 117
RAND_MAX ......................................................98, 115
Range ...................................................................... 86
Range Error27, 119, 120, 165, 166, 167, 168, 177, 178,
.................................................... 186, 187, 190, 191
read ........................................................................ 202
Reading, Recommended ........................................... 7
realloc .............................................................108, 115
Reallocate Memory ................................................ 115
Rebuilding the libpic30 library ................................ 198
Registered Functions ........................................99, 107
Remainder
Double Floating Point ..................................... 171
Single Floating Point ....................................... 173
Remainder Functions
fmod................................................................ 171
fmodf ............................................................... 173
remove ..............................................................83, 204
rename ..............................................................83, 204
Reset.................................................................98, 121
Reset File Pointer .................................................... 84
rewind .........................................................84, 91, 201
Rounding Mode........................................................ 31
S
sbrk .................................................................200, 202
Scan Formats........................................................... 47
scanf ...................................................................47, 85
SCHAR_MAX........................................................... 34
SCHAR_MIN ............................................................ 34
 2004-2014 Microchip Technology Inc.
Search Functions
memchr ........................................................... 122
strchr ............................................................... 129
strcspn ............................................................ 132
strpbrk ............................................................. 139
strrchr.............................................................. 140
strspn .............................................................. 141
strstr ................................................................ 142
strtok ............................................................... 143
Second ............................................ 145, 146, 148, 151
Seed............................................................... 115, 117
Seek
From Beginning of File...................................... 70
From Current Position....................................... 70
From End Of File............................................... 70
SEEK_CUR ........................................................ 51, 70
SEEK_END ........................................................ 51, 70
SEEK_SET......................................................... 51, 70
setbuf ............................................................47, 50, 87
setjmp....................................................................... 36
setjmp.h.................................................................... 36
jmp_buf ............................................................. 36
longjmp ............................................................. 36
setjmp ............................................................... 36
setlocale ................................................................... 35
setvbuf...........................................................47, 50, 88
short int
Maximum Value ................................................ 34
Minimum Value ................................................. 34
SHRT_MAX.............................................................. 34
SHRT_MIN............................................................... 34
sig_atomic_t ............................................................. 37
SIG_DFL .................................................................. 37
SIG_ERR ................................................................. 37
SIG_IGN................................................................... 37
SIGABRT ................................................................. 38
SIGFPE .................................................................... 38
SIGILL ...................................................................... 39
SIGINT ..................................................................... 39
Signal
Abnormal Termination....................................... 38
Error .................................................................. 37
Floating-Point Error........................................... 38
Ignore................................................................ 37
Illegal Instruction ............................................... 39
Interrupt............................................................. 39
Reporting .......................................................... 41
Termination Request......................................... 40
signal....................................................... 38, 39, 40, 42
Signal Handler.................................................... 37, 42
Signal Handler Type................................................. 37
Signal Handling, See signal.h
signal.h..................................................................... 37
raise .................................................................. 41
sig_atomic_t...................................................... 37
SIG_DFL ........................................................... 37
SIG_ERR .......................................................... 37
SIG_IGN ........................................................... 37
SIGABRT .......................................................... 38
SIGFPE............................................................. 38
DS50001456J-page 261
16-Bit Language Tools Libraries
SIGILL ............................................................... 39
SIGINT .............................................................. 39
signal................................................................. 42
SIGSEGV .......................................................... 40
SIGTERM.......................................................... 40
signed char
Maximum Value ................................................ 34
Minimum Value ................................................. 34
SIGSEGV ................................................................. 40
SIGTERM ................................................................. 40
sim30 simulator ...................................................... 198
sin........................................................................... 188
sine
Double Floating Point...................................... 188
Single Floating Point ....................................... 189
sinf.......................................................................... 189
Single Precision Floating Point
Machine Epsilon................................................ 30
Maximum Exponent (base 10) .......................... 30
Maximum Exponent (base 2) ............................ 31
Maximum Value ................................................ 30
Minimum Exponent (base 10) ........................... 31
Minimum Exponent (base 2) ............................. 31
Minimum Value ................................................. 31
Number of Binary Digits .................................... 30
Number of Decimal Digits ................................. 30
sinh......................................................................... 190
sinhf........................................................................ 191
size ........................................................................... 80
size_t ............................................. 45, 50, 97, 122, 145
sizeof ............................................. 45, 50, 97, 122, 145
Sort, Quick ............................................................. 114
Source File Name..................................................... 17
Source Line Number ................................................ 17
Space ....................................................................... 79
Space Character
Defined.............................................................. 23
Test for .............................................................. 23
Specifiers ........................................................... 79, 85
sprintf ................................................................. 47, 89
sqrt ......................................................................... 192
sqrtf ........................................................................ 193
Square Root Function
Double Floating Point...................................... 192
Single Floating Point ....................................... 193
Square Root Functions
sqrt .................................................................. 192
sqrtf ................................................................. 193
srand ...................................................................... 117
sscanf ................................................................. 47, 89
Stack ...................................................................... 200
Standard C Libraries ................................................ 15
Standard C Locale ................................................... 18
Standard Error.................................................... 47, 51
Standard Input.................................................... 47, 52
Standard Output ................................................. 47, 52
Start-up .................................................................... 47
Module, Alternate .............................................. 12
Module, Primary ................................................ 12
stdarg.h .................................................................... 43
DS50001456J-page 262
va_arg ............................................................... 43
va_end .............................................................. 45
va_list ................................................................ 43
va_start ............................................................. 45
stddef.h..................................................................... 45
NULL ................................................................. 45
offsetof .............................................................. 46
ptrdiff_t .............................................................. 45
size_t................................................................. 45
wchar_t.............................................................. 45
stderr .......................................................17, 47, 51, 78
stdin................................................... 47, 51, 52, 77, 85
stdio.h............................................................... 47, 204
_IOFBF.............................................................. 50
_IOLBF.............................................................. 50
_IONBF ............................................................. 50
BUFSIZ ............................................................. 50
clearerr .............................................................. 53
EOF................................................................... 50
fclose................................................................. 54
fdopen ............................................................... 55
feof .................................................................... 57
ferror.................................................................. 58
fflush.................................................................. 59
fgetc .................................................................. 59
fgetpos .............................................................. 60
fgets .................................................................. 61
FILE................................................................... 50
FILENAME_MAX .............................................. 51
fopen ................................................................. 62
FOPEN_MAX .................................................... 51
fpos_t ................................................................ 50
fprintf ................................................................. 64
fputc .................................................................. 65
fputs .................................................................. 65
fread .................................................................. 66
freopen .............................................................. 68
fscanf................................................................. 68
fseek.................................................................. 70
fsetpos............................................................... 71
ftell..................................................................... 73
fwrite.................................................................. 74
getc ................................................................... 76
getchar .............................................................. 77
gets ................................................................... 77
L_tmpnam ......................................................... 51
NULL ................................................................. 51
perror................................................................. 78
printf .................................................................. 79
putc ................................................................... 81
putchar .............................................................. 82
puts ................................................................... 82
remove .............................................................. 83
rename .............................................................. 83
rewind................................................................ 84
scanf.................................................................. 85
SEEK_CUR ....................................................... 51
SEEK_END ....................................................... 51
SEEK_SET........................................................ 51
setbuf ................................................................ 87
 2004-2014 Microchip Technology Inc.
Index
setvbuf .............................................................. 88
size_t ................................................................ 50
sprintf ................................................................ 89
sscanf ............................................................... 89
stderr................................................................. 51
stdin .................................................................. 52
stdout ................................................................ 52
TMP_MAX ........................................................ 52
tmpfile ............................................................... 90
tmpnam ............................................................. 91
ungetc ............................................................... 91
vasprintf ............................................................ 93
vfprintf ............................................................... 94
vprintf ................................................................ 95
vsprintf .............................................................. 96
stdlib.h...............................................................97, 204
abort.................................................................. 98
abs .................................................................... 99
atexit ................................................................. 99
atof .................................................................. 101
atoi .................................................................. 102
atol .................................................................. 102
bsearch ........................................................... 103
calloc............................................................... 105
div ................................................................... 105
div_t .................................................................. 97
exit .................................................................. 107
EXIT_FAILURE................................................. 97
EXIT_SUCCESS .............................................. 97
free.................................................................. 108
getenv ............................................................. 108
labs ................................................................. 109
ldiv .................................................................. 110
ldiv_t ................................................................. 97
malloc ............................................................. 111
MB_CUR_MAX ................................................. 98
mblen .............................................................. 113
mbstowcs ........................................................ 113
mbtowc ........................................................... 113
NULL................................................................. 98
qsort ................................................................ 114
rand................................................................. 115
RAND_MAX ...................................................... 98
realloc ............................................................. 115
size_t ................................................................ 97
srand ............................................................... 117
strdup .............................................................. 117
strtod ............................................................... 118
strtol ................................................................ 119
strtoul .............................................................. 120
system ............................................................ 121
wchar_t ............................................................. 97
wctomb ........................................................... 121
wxstombs ........................................................ 121
stdout ................................................ 47, 51, 52, 79, 82
strcat ...................................................................... 128
strchr ...................................................................... 129
strcmp .................................................................... 130
strcoll...................................................................... 131
strcpy ..................................................................... 131
 2004-2014 Microchip Technology Inc.
strcspn.................................................................... 132
strdup ..................................................................... 117
Streams.................................................................... 47
Associate .......................................................... 55
Binary................................................................ 47
Buffering............................................................ 88
Closing ...................................................... 54, 107
Opening ............................................................ 62
Reading From ................................................... 76
Text ................................................................... 47
Writing To.................................................... 74, 81
strerror.................................................................... 133
strftime ................................................................... 150
String
Length ............................................................. 133
Search............................................................. 142
Transform........................................................ 144
String Functions, See string.h
string.h ................................................................... 122
memchr ........................................................... 122
memcmp ......................................................... 123
memcpy .......................................................... 125
memmove ....................................................... 126
memset ........................................................... 127
NULL............................................................... 122
size_t............................................................... 122
strcat ............................................................... 128
strchr ............................................................... 129
strcmp ............................................................. 130
strcoll............................................................... 131
strcpy .............................................................. 131
strcspn ............................................................ 132
strerror ............................................................ 133
strlen ............................................................... 133
strncat ............................................................. 134
strncmp ........................................................... 136
strncpy ............................................................ 137
strpbrk ............................................................. 139
strrchr.............................................................. 140
strspn .............................................................. 141
strstr ................................................................ 142
strtok ............................................................... 143
strxfrm ............................................................. 144
strlen ...................................................................... 133
strncat .................................................................... 134
strncmp .................................................................. 136
strncpy.................................................................... 137
strncpy_p2d16........................................................ 216
strncpy_p2d24........................................................ 217
strpbrk .................................................................... 139
strrchr ..................................................................... 140
strspn ..................................................................... 141
strstr ....................................................................... 142
strtod .............................................................. 101, 118
strtok ...................................................................... 143
strtol ............................................................... 102, 119
strtoul ..................................................................... 120
struct lconv ............................................................... 35
struct tm ................................................................. 145
strxfrm .................................................................... 144
DS50001456J-page 263
16-Bit Language Tools Libraries
Substrings .............................................................. 143
Subtracting Pointers ................................................. 45
Successful Termination ............................................ 97
Support Library....................................................... 197
system ............................................................ 121, 204
T
Tab ........................................................................... 23
tan .......................................................................... 194
tanf ......................................................................... 194
tangent
Double Floating Point...................................... 194
Single Floating Point ....................................... 194
tanh ........................................................................ 195
tanhf ....................................................................... 196
Temporary
File ............................................................ 90, 107
Filename ..................................................... 51, 91
Pointer............................................................. 115
Termination
Request Message ............................................. 40
Request Signal.................................................. 40
Successful......................................................... 97
Unsuccessful..................................................... 97
Text Mode .......................................................... 55, 62
Text Streams ............................................................ 47
Ticks ........................................................145, 146, 148
time ................................................................ 152, 205
Time Difference ...................................................... 148
Time Structure................................................ 145, 150
Time Zone .............................................................. 151
time_t ......................................................145, 150, 152
time.h ............................................................. 145, 205
asctime............................................................ 146
clock ................................................................ 146
clock_t ............................................................. 145
CLOCKS_PER_SEC ...................................... 145
ctime ............................................................... 147
difftime ............................................................ 148
gmtime ............................................................ 148
localtime .......................................................... 149
mktime ............................................................ 150
NULL............................................................... 146
size_t............................................................... 145
strftime ............................................................ 150
struct tm .......................................................... 145
time ................................................................. 152
time_t .............................................................. 145
TMP_MAX ................................................................ 52
tmpfile....................................................................... 90
tmpnam .................................................................... 91
Tokens ................................................................... 143
tolower...................................................................... 25
toupper ..................................................................... 26
Transferring Control ................................................. 36
Transform String..................................................... 144
Trigonometric Functions
acos ................................................................ 155
acosf ............................................................... 156
asin ................................................................. 157
asinf ................................................................ 157
DS50001456J-page 264
atan ................................................................. 158
atan2 ............................................................... 159
atan2f .............................................................. 161
atanf ................................................................ 159
cos................................................................... 163
cosf.................................................................. 164
sin.................................................................... 188
sinf................................................................... 189
tan ................................................................... 194
tanf .................................................................. 194
type..................................................................... 80, 86
U
UCHAR_MAX........................................................... 35
UINT_MAX ............................................................... 35
ULLONG_MAX......................................................... 35
ULONG_MAX........................................................... 35
Underflow Errors 27, 155, 167, 168, 177, 178, 186, 187
ungetc....................................................................... 91
Universal Time Coordinated................................... 148
unsigned char
Maximum Value ................................................ 35
unsigned int
Maximum Value ................................................ 35
unsigned short int
Maximum Value ................................................ 35
Unsuccessful Termination ........................................ 97
Upper Case Alphabetic Character
Convert To ........................................................ 26
Defined.............................................................. 24
Test for .............................................................. 24
USHRT_MAX ........................................................... 35
UTC ........................................................................ 148
Utility Functions, See stdlib.h
V
va_arg ......................................... 43, 45, 93, 94, 95, 96
va_end............................................... 45, 93, 94, 95, 96
va_list ....................................................................... 43
va_start.............................................. 45, 93, 94, 95, 96
Variable Argument Lists, See stdarg.h
Variable Length Argument List .... 43, 45, 93, 94, 95, 96
vasprintf.................................................................... 93
VERBOSE_DEBUGGING ........................................ 17
Vertical Tab .............................................................. 23
vfprintf................................................................. 47, 94
vprintf.................................................................. 47, 95
vsprintf................................................................ 47, 96
W
wait_eedata ............................................................ 209
wchar_t............................................................... 45, 97
wcstombs ............................................................... 121
wctomb ................................................................... 121
Web Site, Microchip ................................................... 8
Week ...................................................................... 151
White Space ......................................85, 101, 102, 118
White-Space Character
Defined.............................................................. 23
Test for .............................................................. 23
wide .......................................................................... 97
 2004-2014 Microchip Technology Inc.
Index
Wide Character ...............................................113, 121
Wide Character String.....................................113, 121
Wide Character Value .............................................. 45
Width........................................................................ 79
width....................................................................79, 85
write ....................................................................... 203
write_eedata_row................................................... 209
write_eedata_word................................................. 209
write_flash_word16 ................................................ 212
write_flash_word24 ................................................ 212
write_flash_word32 ................................................ 213
write_flash_word48 ................................................ 213
write_flash16 .......................................................... 211
write_flash24 .......................................................... 212
Y
Year ........................................................145, 146, 151
Z
Zero........................................................................ 155
Zero, divide by ............................................38, 41, 105
 2004-2014 Microchip Technology Inc.
DS50001456J-page 265
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