C Standard Library header files

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<assert.h> Conditionally compiled macro that compares its argument to zero
<complex.h> (since C99) Complex number arithmetic
<ctype.h> Functions to determine the type contained in character data
<errno.h> Macros reporting error conditions
<fenv.h> (since C99) Floating-point environment
<float.h> Limits of float types
<inttypes.h> (since C99) Format conversion of integer types
<iso646.h> (since C99) Alternative operator spellings
<limits.h> Sizes of basic types
<locale.h> Localization utilities
<math.h> Common mathematics functions
<setjmp.h> Nonlocal jumps
<signal.h> Signal handling
<stdalign.h> (since C11) Type alignment control
<stdarg.h> Variable arguments
<stdatomic.h> (since C11) Atomic types
<stdbool.h> (since C99) Macros supporting type bool
<stddef.h> Common macro definitions
<stdint.h> (since C99) Fixed-width integer types
<stdio.h> Input/output
<stdlib.h> General utilities: memory management, program utilities, string conversions, random numbers
<stdnoreturn.h> (since C11) Non-returning functions
<string.h> String handling
<tgmath.h> (since C99) Type-generic math (macros wrapping math.h and complex.h)
<threads.h> (since C11) Thread library
<time.h> Time/date utilities
<uchar.h> (since C11) UTF-16 and UTF-32 character utilities
<wchar.h> (since C99) Extended multibyte and wide character utilities
<wctype.h> (since C99) Wide character classification and mapping utilities

[edit] See also

C++ documentation for C++ Standard Library header files