Overview

The interface of C standard library is defined by the following collection of headers.

<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 floating-point types

<inttypes.h>

(since C99)

Format conversion of integer types

<iso646.h>

(since C95)

Alternative operator spellings

<limits.h>

Ranges of integer types

<locale.h>

Localization utilities

<math.h>

Common mathematical functions

<setjmp.h>

Nonlocal jumps

<signal.h>

Signal handling

<stdalign.h>

(since C11)

(deprecated in C23)

alignas and alignof convenience macros

<stdarg.h>

Variable arguments

<stdatomic.h>

(since C11)

Atomic operations

<stdbit.h>

(since C23)

Macros to work with the byte and bit representations of types

<stdbool.h>

(since C99)

(deprecated in C23)

Macros for boolean type

<stdckdint.h>

(since C23)

Macros for performing checked integer arithmetic

<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 , algorithms

<stdmchar.h>

(since C29)

Text transcode

<stdnoreturn.h>

(since C11)

(deprecated in C23)

noreturn convenience macro

<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 C95)

Extended multibyte and wide character utilities

<wctype.h>

(since C95)

Functions to determine the type contained in wide character data

Feature test macros C23

Feature test macro __STDC_VERSION_ASSERT_H__

Value	Since	Feature
202311L	C23	<assert.h>

Feature test macro __STDC_VERSION_COMPLEX_H__

Value	Since	Feature
202311L	C23	<complex.h>

Feature test macro __STDC_VERSION_FENV_H__

Value	Since	Feature
202311L	C23	<fenv.h>

Feature test macro __STDC_VERSION_FLOAT_H__

Value	Since	Feature
202311L	C23	<float.h>

Feature test macro __STDC_VERSION_INTTYPES_H__

Value	Since	Feature
202311L	C23	<inttypes.h>

Feature test macro __STDC_VERSION_LIMITS_H__

Value	Since	Feature
202311L	C23	<limits.h>

Feature test macro __STDC_VERSION_MATH_H__

Value	Since	Feature
202311L	C23	<math.h>

Feature test macro __STDC_VERSION_SETJMP_H__

Value	Since	Feature
202311L	C23	<setjmp.h>

Feature test macro __STDC_VERSION_STDARG_H__

Value	Since	Feature
202311L	C23	<stdarg.h>

Feature test macro __STDC_VERSION_STDATOMIC_H__

Value	Since	Feature
202311L	C23	<stdatomic.h>

Feature test macro __STDC_VERSION_STDBIT_H__

Value	Since	Feature
202311L	C23	<stdbit.h>

Feature test macro __STDC_VERSION_STDCKDINT_H__

Value	Since	Feature
202311L	C23	<stdckdint.h>

Feature test macro __STDC_VERSION_STDDEF_H__

Value	Since	Feature
202311L	C23	<stddef.h>

Feature test macro __STDC_VERSION_STDINT_H__

Value	Since	Feature
202311L	C23	<stdint.h>

Feature test macro __STDC_VERSION_STDIO_H__

Value	Since	Feature
202311L	C23	<stdio.h>

Feature test macro __STDC_VERSION_STDLIB_H__

Value	Since	Feature
202311L	C23	<stdlib.h>

Feature test macro __STDC_VERSION_STDMCHAR_H__

Value	Since	Feature
202311L	C23	<stdmchar.h>

Feature test macro __STDC_VERSION_STRING_H__

Value	Since	Feature
202311L	C23	<string.h>

Feature test macro __STDC_VERSION_TGMATH_H__

Value	Since	Feature
202311L	C23	<tgmath.h>

Feature test macro __STDC_VERSION_TIME_H__

Value	Since	Feature
202311L	C23	<time.h>

Feature test macro __STDC_VERSION_UCHAR_H__

Value	Since	Feature
202311L	C23	<uchar.h>

Feature test macro __STDC_VERSION_WCHAR_H__

Value	Since	Feature
202311L	C23	<wchar.h>

References

• C23 standard (ISO/IEC 9899:2024):
  • 7.1.2 Standard headers (p: 191-192)
• C17 standard (ISO/IEC 9899:2018):
  • 7.1.2 Standard headers (p: 131-132)
• C11 standard (ISO/IEC 9899:2011):
  • 7.1.2 Standard headers (p: 181-182)
• C99 standard (ISO/IEC 9899:1999):
  • 7.1.2 Standard headers (p: 165)
• C89/C90 standard (ISO/IEC 9899:1990):
  • 4.1.2 Standard headers