Fixed width integer types (since C99)

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C
 
Type support
(C23)
(C11)
Numeric limits
Fixed width integer types (C99)
 

Types

Defined in header <stdint.h>
int8_t
int16_t
int32_t
int64_t 		signed integer type with width of
exactly 8, 16, 32 and 64 bits respectively
with no padding bits and using 2's complement for negative values
(provided only if the implementation directly supports the type)
int_fast8_t
int_fast16_t
int_fast32_t
int_fast64_t 		fastest signed integer type with width of
at least 8, 16, 32 and 64 bits respectively
int_least8_t
int_least16_t
int_least32_t
int_least64_t 		smallest signed integer type with width of
at least 8, 16, 32 and 64 bits respectively
intmax_t maximum width integer type
intptr_t integer type capable of holding a pointer
uint8_t
uint16_t
uint32_t
uint64_t 		unsigned integer type with width of
exactly 8, 16, 32 and 64 bits respectively
(provided only if the implementation directly supports the type)
uint_fast8_t
uint_fast16_t
uint_fast32_t
uint_fast64_t 		fastest unsigned integer type with width of
at least 8, 16, 32 and 64 bits respectively
uint_least8_t
uint_least16_t
uint_least32_t
uint_least64_t 		smallest unsigned integer type with width of
at least 8, 16, 32 and 64 bits respectively
uintmax_t maximum width unsigned integer type
uintptr_t unsigned integer type capable of holding a pointer

The implementation may define typedef names intN_t, int_fastN_t, int_leastN_t, uintN_t, uint_fastN_t, and uint_leastN_t when N is not 8, 16, 32 or 64. Typedef names of the form intN_t may only be defined if the implementation supports an integer type of that width with no padding. Thus, uint24_t denotes an unsigned integer type with a width of exactly 24 bits.

Each of the macros listed in below is defined if and only if the implementation defines the corresponding typedef name. The macros INTN_C and UINTN_C correspond to the typedef names int_leastN_t and uint_leastN_t, respectively.

Macro constants

Defined in header <stdint.h>
Signed integers : width
INT8_WIDTHINT16_WIDTHINT32_WIDTHINT64_WIDTH
(C23)(optional)
 bit width of an object of type int8_t, int16_t, int32_t, int64_t (exactly 8, 16, 32, 64)
(macro constant)
INT_FAST8_WIDTHINT_FAST16_WIDTHINT_FAST32_WIDTHINT_FAST64_WIDTH
(C23)
 bit width of an object of type int_fast8_t, int_fast16_t, int_fast32_t, int_fast64_t
(macro constant)
INT_LEAST8_WIDTHINT_LEAST16_WIDTHINT_LEAST32_WIDTHINT_LEAST64_WIDTH
(C23)
 bit width of an object of type int_least8_t, int_least16_t, int_least32_t, int_least64_t
(macro constant)
INTPTR_WIDTH
(C23)(optional)
 bit width of an object of type intptr_t
(macro constant)
INTMAX_WIDTH
(C23)
 bit width of an object of type intmax_t
(macro constant)
Signed integers : minimum value
INT8_MININT16_MININT32_MININT64_MIN
 minimum value of an object of type int8_t, int16_t, int32_t, int64_t
(macro constant)
INT_FAST8_MININT_FAST16_MININT_FAST32_MININT_FAST64_MIN
 minimum value of an object of type int_fast8_t, int_fast16_t, int_fast32_t, int_fast64_t
(macro constant)
INT_LEAST8_MININT_LEAST16_MININT_LEAST32_MININT_LEAST64_MIN
 minimum value of an object of type int_least8_t, int_least16_t, int_least32_t, int_least64_t
(macro constant)
INTPTR_MIN
 minimum value of an object of type intptr_t
(macro constant)
INTMAX_MIN
 minimum value of an object of type intmax_t
(macro constant)
Signed integers : maximum value
INT8_MAXINT16_MAXINT32_MAXINT64_MAX
 maximum value of an object of type int8_t, int16_t, int32_t, int64_t
(macro constant)
INT_FAST8_MAXINT_FAST16_MAXINT_FAST32_MAXINT_FAST64_MAX
 maximum value of an object of type int_fast8_t, int_fast16_t, int_fast32_t, int_fast64_t
(macro constant)
INT_LEAST8_MAXINT_LEAST16_MAXINT_LEAST32_MAXINT_LEAST64_MAX
 maximum value of an object of type int_least8_t, int_least16_t, int_least32_t, int_least64_t
(macro constant)
INTPTR_MAX
 maximum value of an object of type intptr_t
(macro constant)
INTMAX_MAX
 maximum value of an object of type intmax_t
(macro constant)
Unsigned integers : width
UINT8_WIDTHUINT16_WIDTHUINT32_WIDTHUINT64_WIDTH
(C23)(optional)
 bit width of an object of type uint8_t, uint16_t, uint32_t, uint64_t (exactly 8, 16, 32, 64)
(macro constant)
UINT_FAST8_WIDTHUINT_FAST16_WIDTHUINT_FAST32_WIDTHUINT_FAST64_WIDTH
(C23)
 bit width of an object of type uint_fast8_t, uint_fast16_t, uint_fast32_t, uint_fast64_t
(macro constant)
UINT_LEAST8_WIDTHUINT_LEAST16_WIDTHUINT_LEAST32_WIDTHUINT_LEAST64_WIDTH
(C23)
 bit width of an object of type uint_least8_t, uint_least16_t, uint_least32_t, uint_least64_t
(macro constant)
UINTPTR_WIDTH
(C23)(optional)
 bit width of an object of type uintptr_t
(macro constant)
UINTMAX_WIDTH
(C23)
 bit width of an object of type uintmax_t
(macro constant)
Unsigned integers : maximum value
UINT8_MAXUINT16_MAXUINT32_MAXUINT64_MAX
 maximum value of an object of type uint8_t, uint16_t, uint32_t, uint64_t
(macro constant)
UINT_FAST8_MAXUINT_FAST16_MAXUINT_FAST32_MAXUINT_FAST64_MAX
 maximum value of an object of type uint_fast8_t, uint_fast16_t, uint_fast32_t, uint_fast64_t
(macro constant)
UINT_LEAST8_MAXUINT_LEAST16_MAXUINT_LEAST32_MAXUINT_LEAST64_MAX
 maximum value of an object of type uint_least8_t, uint_least16_t, uint_least32_t, uint_least64_t
(macro constant)
UINTPTR_MAX
 maximum value of an object of type uintptr_t
(macro constant)
UINTMAX_MAX
 maximum value of an object of type uintmax_t
(macro constant)

Function macros for minimum-width integer constants

INT8_CINT16_CINT32_CINT64_C
 expands to an integer constant expression having the value specified by its argument and the type int_least8_t, int_least16_t, int_least32_t, int_least64_t respectively
(function macro)
INTMAX_C
 expands to an integer constant expression having the value specified by its argument and the type intmax_t
(function macro)
UINT8_CUINT16_CUINT32_CUINT64_C
 expands to an integer constant expression having the value specified by its argument and the type uint_least8_t, uint_least16_t, uint_least32_t, uint_least64_t respectively
(function macro)
UINTMAX_C
 expands to an integer constant expression having the value specified by its argument and the type uintmax_t
(function macro) 
#include <stdint.h>
UINT64_C(0x123) // might expand to 0x123ULL or 0x123UL

Format macro constants

Defined in header <inttypes.h>

Format constants for the fprintf family of functions

Each of the PRI macros listed here is defined if and only if the implementation defines the corresponding typedef name.

Equivalent
for int or
unsigned int 		Description Macros for data types




[u]intx_t
[u]int_leastx_t
[u]int_fastx_t
[u]intmax_t
[u]intptr_t
d output of a signed decimal integer value PRIdx PRIdLEASTx PRIdFASTx PRIdMAX PRIdPTR
i PRIix PRIiLEASTx PRIiFASTx PRIiMAX PRIiPTR
u output of an unsigned decimal integer value PRIux PRIuLEASTx PRIuFASTx PRIuMAX PRIuPTR
o output of an unsigned octal integer value PRIox PRIoLEASTx PRIoFASTx PRIoMAX PRIoPTR
x output of an unsigned lowercase hexadecimal integer value PRIxx PRIxLEASTx PRIxFASTx PRIxMAX PRIxPTR
X output of an unsigned uppercase hexadecimal integer value PRIXx PRIXLEASTx PRIXFASTx PRIXMAX PRIXPTR

Format constants for the fscanf family of functions

Each of the SCN macros listed in here is defined if and only if the implementation defines the corresponding typedef name and has a suitable fscanf length modifier for the type.

Equivalent
for int or
unsigned int 		Description Macros for data types




[u]intx_t
[u]int_leastx_t
[u]int_fastx_t
[u]intmax_t
[u]intptr_t
d input of a signed decimal integer value SCNdx SCNdLEASTx SCNdFASTx SCNdMAX SCNdPTR
i input of a signed integer value (base is determined by the first characters parsed) SCNix SCNiLEASTx SCNiFASTx SCNiMAX SCNiPTR
u input of an unsigned decimal integer value SCNux SCNuLEASTx SCNuFASTx SCNuMAX SCNuPTR
o input of an unsigned octal integer value SCNox SCNoLEASTx SCNoFASTx SCNoMAX SCNoPTR
x input of an unsigned hexadecimal integer value SCNxx SCNxLEASTx SCNxFASTx SCNxMAX SCNxPTR

Example

See also C++ compatibility note regarding spaces before format macros used in this example.

Run this code
#include <inttypes.h>
#include <stdio.h>
 
int main(void)
{
    printf("%zu\n", sizeof(int64_t));
    printf("%s\n", PRId64);
    printf("%+" PRId64 "\n", INT64_MIN);
    printf("%+" PRId64 "\n", INT64_MAX);
 
    int64_t n = 7;
    printf("%+" PRId64 "\n", n);
}

Possible output: 

8
lld
-9223372036854775808
+9223372036854775807
+7

References

  • C23 standard (ISO/IEC 9899:2024):
  • 7.8.1 Macros for format specifiers (p: TBD)
  • 7.18 Integer types <stdint.h> (p: TBD)
  • C17 standard (ISO/IEC 9899:2018):
  • 7.8.1 Macros for format specifiers (p: 158-159)
  • 7.18 Integer types <stdint.h> (p: 212-216)
  • C11 standard (ISO/IEC 9899:2011):
  • 7.8.1 Macros for format specifiers (p: 217-218)
  • 7.18 Integer types <stdint.h> (p: 289-295)
  • C99 standard (ISO/IEC 9899:1999):
  • 7.8.1 Macros for format specifiers (p: 198-199)
  • 7.18 Integer types <stdint.h> (p: 255-261)

See also

C++ documentation for Fixed width integer types
C++ documentation for User-defined literals (formatting macros note)
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