<html lang="en">
<head>
<title>ISO C - 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="Standards-and-Portability.html#Standards-and-Portability" title="Standards and Portability">
<link rel="next" href="POSIX.html#POSIX" title="POSIX">
<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="ISO-C"></a>
<p>
Next:&nbsp;<a rel="next" accesskey="n" href="POSIX.html#POSIX">POSIX</a>,
Up:&nbsp;<a rel="up" accesskey="u" href="Standards-and-Portability.html#Standards-and-Portability">Standards and Portability</a>
<hr>
</div>

<h4 class="subsection">1.2.1 ISO C</h4>

<p><a name="index-ISO-C-3"></a>
The GNU C library is compatible with the C standard adopted by the
American National Standards Institute (ANSI):
<cite>American National Standard X3.159-1989&mdash;&ldquo;ANSI C&rdquo;</cite> and later
by the International Standardization Organization (ISO):
<cite>ISO/IEC 9899:1990, &ldquo;Programming languages&mdash;C&rdquo;</cite>. 
We here refer to the standard as ISO&nbsp;C<!-- /@w --> since this is the more
general standard in respect of ratification. 
The header files and library facilities that make up the GNU library are
a superset of those specified by the ISO&nbsp;C<!-- /@w --> standard.

   <p><a name="index-gcc-4"></a>If you are concerned about strict adherence to the ISO&nbsp;C<!-- /@w --> standard, you
should use the &lsquo;<samp><span class="samp">-ansi</span></samp>&rsquo; option when you compile your programs with
the GNU C compiler.  This tells the compiler to define <em>only</em> ISO
standard features from the library header files, unless you explicitly
ask for additional features.  See <a href="Feature-Test-Macros.html#Feature-Test-Macros">Feature Test Macros</a>, for
information on how to do this.

   <p>Being able to restrict the library to include only ISO&nbsp;C<!-- /@w --> features is
important because ISO&nbsp;C<!-- /@w --> puts limitations on what names can be defined
by the library implementation, and the GNU extensions don't fit these
limitations.  See <a href="Reserved-Names.html#Reserved-Names">Reserved Names</a>, for more information about these
restrictions.

   <p>This manual does not attempt to give you complete details on the
differences between ISO&nbsp;C<!-- /@w --> and older dialects.  It gives advice on how
to write programs to work portably under multiple C dialects, but does
not aim for completeness.

   </body></html>