arm-2011.03/share/doc/arm-arm-none-linux-gnueabi/html/libc/Integers.html - nest-cam/v350/arm-none-linux-gnueabi-i686-pc-linux-gnu - Git at Google

 <html lang="en">
 <head>
 <title>Integers - The GNU C Library</title>
 <meta http-equiv="Content-Type" content="text/html">
 <meta name="description" content="The GNU C Library">
 <meta name="generator" content="makeinfo 4.13">
 <link title="Top" rel="start" href="index.html#Top">
 <link rel="up" href="Arithmetic.html#Arithmetic" title="Arithmetic">
 <link rel="next" href="Integer-Division.html#Integer-Division" title="Integer Division">
 <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
 <!--
 This file documents the GNU C library.

 This is Edition 0.12, last updated 2007-10-27,
 of `The GNU C Library Reference Manual', for version
 2.8 (Sourcery G++ Lite 2011.03-41).

 Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2001, 2002,
 2003, 2007, 2008, 2010 Free Software Foundation, Inc.

 Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.3 or
 any later version published by the Free Software Foundation; with the
 Invariant Sections being ``Free Software Needs Free Documentation''
 and ``GNU Lesser General Public License'', the Front-Cover texts being
 ``A GNU Manual'', and with the Back-Cover Texts as in (a) below.  A
 copy of the license is included in the section entitled "GNU Free
 Documentation License".

 (a) The FSF's Back-Cover Text is: ``You have the freedom to
 copy and modify this GNU manual.  Buying copies from the FSF
 supports it in developing GNU and promoting software freedom.''-->
 <meta http-equiv="Content-Style-Type" content="text/css">
 <style type="text/css"><!--
   pre.display { font-family:inherit }
   pre.format  { font-family:inherit }
   pre.smalldisplay { font-family:inherit; font-size:smaller }
   pre.smallformat  { font-family:inherit; font-size:smaller }
   pre.smallexample { font-size:smaller }
   pre.smalllisp    { font-size:smaller }
   span.sc    { font-variant:small-caps }
   span.roman { font-family:serif; font-weight:normal; }
   span.sansserif { font-family:sans-serif; font-weight:normal; }
 --></style>
 <link rel="stylesheet" type="text/css" href="../cs.css">
 </head>
 <body>
 <div class="node">
 <a name="Integers"></a>
 <p>
 Next:&nbsp;<a rel="next" accesskey="n" href="Integer-Division.html#Integer-Division">Integer Division</a>,
 Up:&nbsp;<a rel="up" accesskey="u" href="Arithmetic.html#Arithmetic">Arithmetic</a>
 <hr>
 </div>

 <h3 class="section">20.1 Integers</h3>

 <p><a name="index-integer-2320"></a>
 The C language defines several integer data types: integer, short integer,
 long integer, and character, all in both signed and unsigned varieties.
 The GNU C compiler extends the language to contain long long integers
 as well.
 <a name="index-signedness-2321"></a>
 The C integer types were intended to allow code to be portable among
 machines with different inherent data sizes (word sizes), so each type
 may have different ranges on different machines.  The problem with
 this is that a program often needs to be written for a particular range
 of integers, and sometimes must be written for a particular size of
 storage, regardless of what machine the program runs on.

    <p>To address this problem, the GNU C library contains C type definitions
 you can use to declare integers that meet your exact needs.  Because the
 GNU C library header files are customized to a specific machine, your
 program source code doesn't have to be.

    <p>These <code>typedef</code>s are in <samp><span class="file">stdint.h</span></samp>.
 <a name="index-stdint_002eh-2322"></a>
 If you require that an integer be represented in exactly N bits, use one
 of the following types, with the obvious mapping to bit size and signedness:

      <ul>
 <li>int8_t
 <li>int16_t
 <li>int32_t
 <li>int64_t
 <li>uint8_t
 <li>uint16_t
 <li>uint32_t
 <li>uint64_t
 </ul>

    <p>If your C compiler and target machine do not allow integers of a certain
 size, the corresponding above type does not exist.

    <p>If you don't need a specific storage size, but want the smallest data
 structure with <em>at least</em> N bits, use one of these:

      <ul>
 <li>int_least8_t
 <li>int_least16_t
 <li>int_least32_t
 <li>int_least64_t
 <li>uint_least8_t
 <li>uint_least16_t
 <li>uint_least32_t
 <li>uint_least64_t
 </ul>

    <p>If you don't need a specific storage size, but want the data structure
 that allows the fastest access while having at least N bits (and
 among data structures with the same access speed, the smallest one), use
 one of these:

      <ul>
 <li>int_fast8_t
 <li>int_fast16_t
 <li>int_fast32_t
 <li>int_fast64_t
 <li>uint_fast8_t
 <li>uint_fast16_t
 <li>uint_fast32_t
 <li>uint_fast64_t
 </ul>

    <p>If you want an integer with the widest range possible on the platform on
 which it is being used, use one of the following.  If you use these,
 you should write code that takes into account the variable size and range
 of the integer.

      <ul>
 <li>intmax_t
 <li>uintmax_t
 </ul>

    <p>The GNU C library also provides macros that tell you the maximum and
 minimum possible values for each integer data type.  The macro names
 follow these examples: <code>INT32_MAX</code>, <code>UINT8_MAX</code>,
 <code>INT_FAST32_MIN</code>, <code>INT_LEAST64_MIN</code>, <code>UINTMAX_MAX</code>,
 <code>INTMAX_MAX</code>, <code>INTMAX_MIN</code>.  Note that there are no macros for
 unsigned integer minima.  These are always zero.
 <a name="index-maximum-possible-integer-2323"></a><a name="index-minimum-possible-integer-2324"></a>
 There are similar macros for use with C's built in integer types which
 should come with your C compiler.  These are described in <a href="Data-Type-Measurements.html#Data-Type-Measurements">Data Type Measurements</a>.

    <p>Don't forget you can use the C <code>sizeof</code> function with any of these
 data types to get the number of bytes of storage each uses.

    </body></html>
	<html lang="en">
	<head>
	<title>Integers - The GNU C Library</title>
	<meta http-equiv="Content-Type" content="text/html">
	<meta name="description" content="The GNU C Library">
	<meta name="generator" content="makeinfo 4.13">
	<link title="Top" rel="start" href="index.html#Top">
	<link rel="up" href="Arithmetic.html#Arithmetic" title="Arithmetic">
	<link rel="next" href="Integer-Division.html#Integer-Division" title="Integer Division">
	<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
	<!--
	This file documents the GNU C library.

	This is Edition 0.12, last updated 2007-10-27,
	of `The GNU C Library Reference Manual', for version
	2.8 (Sourcery G++ Lite 2011.03-41).

	Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2001, 2002,
	2003, 2007, 2008, 2010 Free Software Foundation, Inc.

	Permission is granted to copy, distribute and/or modify this document
	under the terms of the GNU Free Documentation License, Version 1.3 or
	any later version published by the Free Software Foundation; with the
	Invariant Sections being ``Free Software Needs Free Documentation''
	and ``GNU Lesser General Public License'', the Front-Cover texts being
	``A GNU Manual'', and with the Back-Cover Texts as in (a) below. A
	copy of the license is included in the section entitled "GNU Free
	Documentation License".

	(a) The FSF's Back-Cover Text is: ``You have the freedom to
	copy and modify this GNU manual. Buying copies from the FSF
	supports it in developing GNU and promoting software freedom.''-->
	<meta http-equiv="Content-Style-Type" content="text/css">
	<style type="text/css"><!--
	pre.display { font-family:inherit }
	pre.format { font-family:inherit }
	pre.smalldisplay { font-family:inherit; font-size:smaller }
	pre.smallformat { font-family:inherit; font-size:smaller }
	pre.smallexample { font-size:smaller }
	pre.smalllisp { font-size:smaller }
	span.sc { font-variant:small-caps }
	span.roman { font-family:serif; font-weight:normal; }
	span.sansserif { font-family:sans-serif; font-weight:normal; }
	--></style>
	<link rel="stylesheet" type="text/css" href="../cs.css">
	</head>
	<body>
	<div class="node">
	<a name="Integers"></a>
	<p>
	Next: <a rel="next" accesskey="n" href="Integer-Division.html#Integer-Division">Integer Division</a>,
	Up: <a rel="up" accesskey="u" href="Arithmetic.html#Arithmetic">Arithmetic</a>
	<hr>
	</div>

	<h3 class="section">20.1 Integers</h3>

	<p><a name="index-integer-2320"></a>
	The C language defines several integer data types: integer, short integer,
	long integer, and character, all in both signed and unsigned varieties.
	The GNU C compiler extends the language to contain long long integers
	as well.
	<a name="index-signedness-2321"></a>
	The C integer types were intended to allow code to be portable among
	machines with different inherent data sizes (word sizes), so each type
	may have different ranges on different machines. The problem with
	this is that a program often needs to be written for a particular range
	of integers, and sometimes must be written for a particular size of
	storage, regardless of what machine the program runs on.

	<p>To address this problem, the GNU C library contains C type definitions
	you can use to declare integers that meet your exact needs. Because the
	GNU C library header files are customized to a specific machine, your
	program source code doesn't have to be.

	<p>These <code>typedef</code>s are in <samp><span class="file">stdint.h</span></samp>.
	<a name="index-stdint_002eh-2322"></a>
	If you require that an integer be represented in exactly N bits, use one
	of the following types, with the obvious mapping to bit size and signedness:

	<ul>
	<li>int8_t
	<li>int16_t
	<li>int32_t
	<li>int64_t
	<li>uint8_t
	<li>uint16_t
	<li>uint32_t
	<li>uint64_t
	</ul>

	<p>If your C compiler and target machine do not allow integers of a certain
	size, the corresponding above type does not exist.

	<p>If you don't need a specific storage size, but want the smallest data
	structure with <em>at least</em> N bits, use one of these:

	<ul>
	<li>int_least8_t
	<li>int_least16_t
	<li>int_least32_t
	<li>int_least64_t
	<li>uint_least8_t
	<li>uint_least16_t
	<li>uint_least32_t
	<li>uint_least64_t
	</ul>

	<p>If you don't need a specific storage size, but want the data structure
	that allows the fastest access while having at least N bits (and
	among data structures with the same access speed, the smallest one), use
	one of these:

	<ul>
	<li>int_fast8_t
	<li>int_fast16_t
	<li>int_fast32_t
	<li>int_fast64_t
	<li>uint_fast8_t
	<li>uint_fast16_t
	<li>uint_fast32_t
	<li>uint_fast64_t
	</ul>

	<p>If you want an integer with the widest range possible on the platform on
	which it is being used, use one of the following. If you use these,
	you should write code that takes into account the variable size and range
	of the integer.

	<ul>
	<li>intmax_t
	<li>uintmax_t
	</ul>

	<p>The GNU C library also provides macros that tell you the maximum and
	minimum possible values for each integer data type. The macro names
	follow these examples: <code>INT32_MAX</code>, <code>UINT8_MAX</code>,
	<code>INT_FAST32_MIN</code>, <code>INT_LEAST64_MIN</code>, <code>UINTMAX_MAX</code>,
	<code>INTMAX_MAX</code>, <code>INTMAX_MIN</code>. Note that there are no macros for
	unsigned integer minima. These are always zero.
	<a name="index-maximum-possible-integer-2323"></a><a name="index-minimum-possible-integer-2324"></a>
	There are similar macros for use with C's built in integer types which
	should come with your C compiler. These are described in <a href="Data-Type-Measurements.html#Data-Type-Measurements">Data Type Measurements</a>.

	<p>Don't forget you can use the C <code>sizeof</code> function with any of these
	data types to get the number of bytes of storage each uses.

	</body></html>