The C language provides no built-in facilities for performing such
common operations as input/output, memory management, string
manipulation, and the like. Instead, these facilities are defined
in a standard library, which you compile and link with your
programs.
The GNU C library, described in this document, defines all of the
library functions that are specified by the ISO C standard, as well as
additional features specific to POSIX and other derivatives of the Unix
operating system, and extensions specific to the GNU system.
The purpose of this manual is to tell you how to use the facilities
of the GNU library. We have mentioned which features belong to which
standards to help you identify things that are potentially non-portable
to other systems. But the emphasis in this manual is not on strict
portability.
