The most important elements of most modern distributions of Linux. GNU C Library is one of the most important components of most modern Linux distributions. It is used by almost all C programs and provides the most essential program interface.The GNU C library is primarily designed to be portable and high performance library.It C follows all relevant standards (ISO C 99, POSIX. 1c, POSIX.1j, POSIX.1d, Unix98, Single Unix Specification). It also has internationalization and one of the most complete internationalization interfaces known.