=====The Standard C Library=====

C++ programmers have access to a variety of functions from the standard C libraries, as defined in [[http://www.open-std.org/jtc1/sc22/wg14/|ISO/IEC 9899:1990]] (known as [[http://en.wikipedia.org/wiki/ANSI_C|C90]]).  All of the functions in these libraries are defined in the **std** [[keywords/namespace]].

====C Library Functions====

The following is a list of standard C library functions, grouped roughly by functionality:

  * [[c/io/|Standard C I/O]]
  * [[c/string/|Standard C String & Character]]
  * [[c/math/|Standard C Math]]
  * [[c/date/|Standard C Date & Time]]
  * [[c/mem/|Standard C Memory]]
  * [[c/other/|Other standard C functions]]

Alternatively, there is a list of [[all|all standard C library functions]].

====Standard C Header Files====

The functions above are defined in the following 18 header files:

  * <cassert> 
  * <ciso646> 
  * <csetjmp> 
  * <cstdio> 
  * <ctime>
  * <cctype> 
  * <climits> 
  * <csignal> 
  * <cstdlib> 
  * <cwchar>
  * <cerrno> 
  * <clocale> 
  * <cstdarg> 
  * <cstring> 
  * <cwctype>
  * <cfloat> 
  * <cmath> 
  * <cstddef>

When including header files for the standard C libraries, it is preferable to use the ''cfile'' notation instead of the ''file.h'' notation.  For example, the ''stdio.h'' header file should be included using this command:

<code>
  #include <cstdio>
</code>

The ''file.h'' notation works, but it is mainly meant for backwards compatibility.   The difference between the ''cfile'' and ''file.h'' notation is that functions included via the ''file.h'' notation will appear in the global namespace instead of the **std** namespace.

See also: [[http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf|The 2005 C99 working paper]] from the [[http://www.open-std.org/jtc1/sc22/wg14/www/standards.html|Approved Standards of working group 14]].