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The Standard C Library [C++ Reference]
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<li class="level2"><div class="li"><span class="li"><a href="#the_standard_c_library" class="toc">The Standard C Library</a></span></div>
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<li class="level3"><div class="li"><span class="li"><a href="#c_library_functions" class="toc">C Library Functions</a></span></div></li>
<li class="level3"><div class="li"><span class="li"><a href="#standard_c_header_files" class="toc">Standard C Header Files</a></span></div></li></ul>
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<h2><a name="the_standard_c_library" id="the_standard_c_library">The Standard C Library</a></h2>
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<p>
C++ programmers have access to a variety of functions from the standard C libraries, as defined in <a href="http://www.open-std.org/jtc1/sc22/wg14/" class="urlextern" title="http://www.open-std.org/jtc1/sc22/wg14/" rel="nofollow">ISO/IEC 9899:1990</a> (known as <a href="http://en.wikipedia.org/wiki/ANSI_C" class="urlextern" title="http://en.wikipedia.org/wiki/ANSI_C" rel="nofollow">C90</a>). All of the functions in these libraries are defined in the <strong>std</strong> <a href="../keywords/namespace.html" class="wikilink1" title="keywords:namespace">namespace</a>.
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<h3><a name="c_library_functions" id="c_library_functions">C Library Functions</a></h3>
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<p>
The following is a list of standard C library functions, grouped roughly by functionality:
</p>
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<li class="level1"><div class="li"> <a href="../c/io/start.html" class="wikilink1" title="c:io:start">Standard C I/O</a></div>
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<li class="level1"><div class="li"> <a href="../c/string/start.html" class="wikilink1" title="c:string:start">Standard C String & Character</a></div>
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<li class="level1"><div class="li"> <a href="../c/math/start.html" class="wikilink1" title="c:math:start">Standard C Math</a></div>
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<li class="level1"><div class="li"> <a href="../c/date/start.html" class="wikilink1" title="c:date:start">Standard C Date & Time</a></div>
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<li class="level1"><div class="li"> <a href="../c/mem/start.html" class="wikilink1" title="c:mem:start">Standard C Memory</a></div>
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<li class="level1"><div class="li"> <a href="../c/other/start.html" class="wikilink1" title="c:other:start">Other standard C functions</a></div>
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<p>
Alternatively, there is a list of <a href="../c/all.html" class="wikilink1" title="c:all">all standard C library functions</a>.
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<h3><a name="standard_c_header_files" id="standard_c_header_files">Standard C Header Files</a></h3>
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<p>
The functions above are defined in the following 18 header files:
</p>
<ul>
<li class="level1"><div class="li"> <cassert> </div>
</li>
<li class="level1"><div class="li"> <ciso646> </div>
</li>
<li class="level1"><div class="li"> <csetjmp> </div>
</li>
<li class="level1"><div class="li"> <cstdio> </div>
</li>
<li class="level1"><div class="li"> <ctime></div>
</li>
<li class="level1"><div class="li"> <cctype> </div>
</li>
<li class="level1"><div class="li"> <climits> </div>
</li>
<li class="level1"><div class="li"> <csignal> </div>
</li>
<li class="level1"><div class="li"> <cstdlib> </div>
</li>
<li class="level1"><div class="li"> <cwchar></div>
</li>
<li class="level1"><div class="li"> <cerrno> </div>
</li>
<li class="level1"><div class="li"> <clocale> </div>
</li>
<li class="level1"><div class="li"> <cstdarg> </div>
</li>
<li class="level1"><div class="li"> <cstring> </div>
</li>
<li class="level1"><div class="li"> <cwctype></div>
</li>
<li class="level1"><div class="li"> <cfloat> </div>
</li>
<li class="level1"><div class="li"> <cmath> </div>
</li>
<li class="level1"><div class="li"> <cstddef></div>
</li>
</ul>
<p>
When including header files for the standard C libraries, it is preferable to use the <code>cfile</code> notation instead of the <code>file.h</code> notation. For example, the <code>stdio.h</code> header file should be included using this command:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="co2">#include <cstdio></span></pre>
<p>
The <code>file.h</code> notation works, but it is mainly meant for backwards compatibility. The difference between the <code>cfile</code> and <code>file.h</code> notation is that functions included via the <code>file.h</code> notation will appear in the global namespace instead of the <strong>std</strong> namespace.
</p>
<p>
See also: <a href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf" class="urlextern" title="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf" rel="nofollow">The 2005 C99 working paper</a> from the <a href="http://www.open-std.org/jtc1/sc22/wg14/www/standards.html" class="urlextern" title="http://www.open-std.org/jtc1/sc22/wg14/www/standards.html" rel="nofollow">Approved Standards of working group 14</a>.
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