C standard library

The C standard library or libc is the standard library for the C programming language, as specified in the ISO C standard. Starting from the original ANSI C standard, it was developed at the same time as the C library POSIX specification, which is a superset of it. Since ANSI C was adopted by the International Organization for Standardization, the C standard library is also called the ISO C library. The C standard library provides macros, type definitions and functions for tasks such as string handling, mathematical computations, input/output processing, memory management, and several other operating system services. The application programming interface (API) of the C standard library is declared in a number of s. Each header file contains one or more function declarations, data type definitions, and macros. After a long period of stability, three new header files (iso646.h, wchar.h, and wctype.h) were added with Normative Addendum 1 (NA1), an addition to the C Standard ratified in 1995. Six more header files (complex.h, fenv.h, inttypes.h, stdbool.h, stdint.h, and tgmath.h) were added with C99, a revision to the C Standard published in 1999, and five more files (stdalign.h, stdatomic.h, stdnoreturn.h, threads.h, and uchar.h) with C11 in 2011. In total, there are now 29 header files: Three of the header files (complex.h, stdatomic.h, and threads.h) are conditional features that implementations are not required to support. The POSIX standard added several nonstandard C headers for Unix-specific functionality. Many have found their way to other architectures. Examples include fcntl.h and unistd.h. A number of other groups are using other nonstandard headers – the GNU C Library has alloca.h, and HP OpenVMS has the va_count() function. On Unix-like systems, the authoritative documentation of the actually implemented API is provided in the form of man pages. On most systems, man pages on standard library functions are in section 3; section 7 may contain some more generic pages on underlying concepts (e.g.