C Programming/Standard library reference

Headers

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ANSI C (C89)/ISO C (C90)

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assert.h Verify program assertion file
ctype.h Character types file.
errno.h System error numbers file
float.h Floating types file
limits.h Implementation-defined constants file.
locale.h Category macros file.
math.h Mathematical declarations file.
setjmp.h Stack environment declarations file.
signal.h Signals file.
stdarg.h Handle variable argument list file.
stddef.h Standard type definitions file.
stdio.h Standard buffered input/output file.
stdlib.h Standard library definitions file.
string.h String operations file.
time.h Time types file.

ISO C (C94/C95), Amendment 1 (AMD1)

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Very old compilers may not include some or all of these headers

iso646.h Alternative spellings.
wchar.h Wide-character handling.
wctype.h Wide-character classification and mapping utilities.

ISO C (C99)

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These are supported only in newer compilers

complex.h Complex arithmetic.
fenv.h Floating-point environment.
inttypes.h Fixed size integer types.
stdbool.h Boolean type and values.
stdint.h Integer types.
tgmath.h Type-generic macros.

ISO C (C11)

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These are supported only in newer compilers

stdalign.h Alignment keywords and macros.
stdatomic.h Atomic operations on data shared between threads.
stdnoreturn.h _Noreturn function specifier macro.
threads.h Support for multiple threads of execution.
uchar.h Types and functions for manipulating Unicode characters.

Table of functions

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This table also includes function-like macros