C Standard Library headers

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> (C99)	Complex number arithmetic
<ctype.h>	Functions to determine the type contained in character data
<errno.h>	Macros reporting error conditions
<fenv.h> (C99)	Floating-point environment
<float.h>	Limits of floating-point types
<inttypes.h> (C99)	Format conversion of integer types
<iso646.h> (C95)	Alternative operator spellings
<limits.h>	Ranges of integer types
<locale.h>	Localization utilities
<math.h>	Common mathematics 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> (C11)	Atomic operations
<stdbit.h> (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> (C23)	Macros for performing checked integer arithmetic
<stddef.h>	Common macro definitions
<stdint.h> (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> (C99)	Type-generic math (macros wrapping <math.h> and <complex.h> )
<threads.h> (C11)	Thread library
<time.h>	Time/date utilities
<uchar.h> (C11)	UTF-16 and UTF-32 character utilities
<wchar.h> (C95)	Extended multibyte and wide character utilities
<wctype.h> (C95)	Functions to determine the type contained in wide character data

Feature test macros (since C23)

Feature test macros are defined in corresponding headers respectively since C23. Note that not all headers contain such a macro.

#	Header	Macro name	Value
1	<assert.h>	__STDC_VERSION_ASSERT_H__	202311L
2	<complex.h>	__STDC_VERSION_COMPLEX_H__	202311L
3	<ctype.h>	N/A
4	<errno.h>	N/A
5	<fenv.h>	__STDC_VERSION_FENV_H__	202311L
6	<float.h>	__STDC_VERSION_FLOAT_H__	202311L
7	<inttypes.h>	__STDC_VERSION_INTTYPES_H__	202311L
8	<iso646.h>	N/A
9	<limits.h>	__STDC_VERSION_LIMITS_H__	202311L
10	<locale.h>	N/A
11	<math.h>	__STDC_VERSION_MATH_H__	202311L
12	<setjmp.h>	__STDC_VERSION_SETJMP_H__	202311L
13	<signal.h>	N/A
14	<stdalign.h>	N/A
15	<stdarg.h>	__STDC_VERSION_STDARG_H__	202311L
16	<stdatomic.h>	__STDC_VERSION_STDATOMIC_H__	202311L
17	<stdbit.h>	__STDC_VERSION_STDBIT_H__	202311L
18	<stdbool.h>	N/A
19	<stdckdint.h>	__STDC_VERSION_STDCKDINT_H__	202311L
20	<stddef.h>	__STDC_VERSION_STDDEF_H__	202311L
21	<stdint.h>	__STDC_VERSION_STDINT_H__	202311L
22	<stdio.h>	__STDC_VERSION_STDIO_H__	202311L
23	<stdlib.h>	__STDC_VERSION_STDLIB_H__	202311L
24	<stdmchar.h>	__STDC_VERSION_STDMCHAR_H__	2029 ?? L
25	<stdnoreturn.h>	N/A
26	<string.h>	__STDC_VERSION_STRING_H__	202311L
27	<tgmath.h>	__STDC_VERSION_TGMATH_H__	202311L
28	<threads.h>	N/A
29	<time.h>	__STDC_VERSION_TIME_H__	202311L
30	<uchar.h>	__STDC_VERSION_UCHAR_H__	202311L
31	<wchar.h>	__STDC_VERSION_WCHAR_H__	202311L
32	<wctype.h>	N/A

References

See also

C++ documentation for Standard Library headers