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Numeric limits

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[edit] Limits of integer types

Limits of core language integer types
Defined in header <limits.h>
BOOL_WIDTH
(C23)
bit width of _Bool
(macro constant)
CHAR_BIT
number of bits in a byte
(macro constant) [edit]
MB_LEN_MAX
maximum number of bytes in a multibyte character
(macro constant) [edit]
CHAR_WIDTH
(C23)
bit width of char, same as CHAR_BIT
(macro constant)
CHAR_MIN
minimum value of char
(macro constant) [edit]
CHAR_MAX
maximum value of char
(macro constant) [edit]
SCHAR_WIDTHSHRT_WIDTHINT_WIDTHLONG_WIDTHLLONG_WIDTH
(C23)(C23)(C23)(C23)(C23)
bit width of signed char, short, int, long, and long long respectively
(macro constant)
SCHAR_MINSHRT_MININT_MINLONG_MINLLONG_MIN
(C99)
minimum value of signed char, short, int, long and long long respectively
(macro constant) [edit]
SCHAR_MAXSHRT_MAXINT_MAXLONG_MAXLLONG_MAX
(C99)
maximum value of signed char, short, int, long and long long respectively
(macro constant) [edit]
UCHAR_WIDTHUSHRT_WIDTHUINT_WIDTHULONG_WIDTHULLONG_WIDTH
(C23)(C23)(C23)(C23)(C23)
bit width of unsigned char, unsigned short, unsigned int, unsigned long, and unsigned long long respectively
(macro constant)
UCHAR_MAXUSHRT_MAXUINT_MAXULONG_MAXULLONG_MAX
(C99)
maximum value of unsigned char, unsigned short, unsigned int,
unsigned long and unsigned long long respectively
(macro constant) [edit]
BITINT_MAXWIDTH
(C23)
maximum width N supported by the declaration of a bit-precise integer in the type specifier _BitInt(N), greater than or equal to ULLONG_WIDTH
(macro constant)
Limits of library type aliases
Defined in header <stdint.h>
PTRDIFF_WIDTH
(C23)
bit width of object of ptrdiff_t type
(macro constant)
PTRDIFF_MIN
(C99)
minimum value of ptrdiff_t
(macro constant) [edit]
PTRDIFF_MAX
(C99)
maximum value of ptrdiff_t
(macro constant) [edit]
SIZE_WIDTH
(C23)
bit width of object of size_t type
(macro constant)
SIZE_MAX
(C99)
maximum value of size_t
(macro constant) [edit]
SIG_ATOMIC_WIDTH
(C23)
bit width of object of sig_atomic_t type
(macro constant)
SIG_ATOMIC_MIN
(C99)
minimum value of sig_atomic_t
(macro constant) [edit]
SIG_ATOMIC_MAX
(C99)
maximum value of sig_atomic_t
(macro constant) [edit]
WINT_WIDTH
(C23)
bit width of object of wint_t type
(macro constant)
WINT_MIN
(C99)
minimum value of wint_t
(macro constant) [edit]
WINT_MAX
(C99)
maximum value of wint_t
(macro constant) [edit]
Defined in header <wchar.h>
Defined in header <stdint.h>
WCHAR_WIDTH
(C23)
bit width of object of wchar_t type
(macro constant)
WCHAR_MIN
(C99)
minimum value of wchar_t
(macro constant) [edit]
WCHAR_MAX
(C99)
maximum value of wchar_t
(macro constant) [edit]

[edit] Notes

The types of these constants, other than CHAR_BIT and MB_LEN_MAX, are required to match the results of the integral promotions as applied to objects of the types they describe: CHAR_MAX may have type int or unsigned int, but never char. Similarly USHRT_MAX may not be of an unsigned type: its type may be int.

A freestanding implementation may lack sig_atomic_t and/or wint_t typedef names, in which case the SIG_ATOMIC_* and/or WINT_* macros are correspondingly absent.

[edit] Example

#include <limits.h>
#include <stdint.h>
#include <stdio.h>
 
int main(void)
{
    printf("CHAR_BIT       = %d\n", CHAR_BIT);
    printf("MB_LEN_MAX     = %d\n\n", MB_LEN_MAX);
 
    printf("CHAR_MIN       = %+d\n", CHAR_MIN);
    printf("CHAR_MAX       = %+d\n", CHAR_MAX);
    printf("SCHAR_MIN      = %+d\n", SCHAR_MIN);
    printf("SCHAR_MAX      = %+d\n", SCHAR_MAX);
    printf("UCHAR_MAX      = %u\n\n", UCHAR_MAX);
 
    printf("SHRT_MIN       = %+d\n", SHRT_MIN);
    printf("SHRT_MAX       = %+d\n", SHRT_MAX);
    printf("USHRT_MAX      = %u\n\n", USHRT_MAX);
 
    printf("INT_MIN        = %+d\n", INT_MIN);
    printf("INT_MAX        = %+d\n", INT_MAX);
    printf("UINT_MAX       = %u\n\n", UINT_MAX);
 
    printf("LONG_MIN       = %+ld\n", LONG_MIN);
    printf("LONG_MAX       = %+ld\n", LONG_MAX);
    printf("ULONG_MAX      = %lu\n\n", ULONG_MAX);
 
    printf("LLONG_MIN      = %+lld\n", LLONG_MIN);
    printf("LLONG_MAX      = %+lld\n", LLONG_MAX);
    printf("ULLONG_MAX     = %llu\n\n", ULLONG_MAX);
 
    printf("PTRDIFF_MIN    = %td\n", PTRDIFF_MIN);
    printf("PTRDIFF_MAX    = %+td\n", PTRDIFF_MAX);
    printf("SIZE_MAX       = %zu\n", SIZE_MAX);
    printf("SIG_ATOMIC_MIN = %+jd\n",(intmax_t)SIG_ATOMIC_MIN);
    printf("SIG_ATOMIC_MAX = %+jd\n",(intmax_t)SIG_ATOMIC_MAX);
    printf("WCHAR_MIN      = %+jd\n",(intmax_t)WCHAR_MIN);
    printf("WCHAR_MAX      = %+jd\n",(intmax_t)WCHAR_MAX);
    printf("WINT_MIN       = %jd\n", (intmax_t)WINT_MIN);
    printf("WINT_MAX       = %jd\n", (intmax_t)WINT_MAX);
}

Possible output:

CHAR_BIT       = 8
MB_LEN_MAX     = 16
 
CHAR_MIN       = -128
CHAR_MAX       = +127
SCHAR_MIN      = -128
SCHAR_MAX      = +127
UCHAR_MAX      = 255
 
SHRT_MIN       = -32768
SHRT_MAX       = +32767
USHRT_MAX      = 65535
 
INT_MIN        = -2147483648
INT_MAX        = +2147483647
UINT_MAX       = 4294967295
 
LONG_MIN       = -9223372036854775808
LONG_MAX       = +9223372036854775807
ULONG_MAX      = 18446744073709551615
 
LLONG_MIN      = -9223372036854775808
LLONG_MAX      = +9223372036854775807
ULLONG_MAX     = 18446744073709551615
 
PTRDIFF_MIN    = -9223372036854775808
PTRDIFF_MAX    = +9223372036854775807
SIZE_MAX       = 18446744073709551615
SIG_ATOMIC_MIN = -2147483648
SIG_ATOMIC_MAX = +2147483647
WCHAR_MIN      = -2147483648
WCHAR_MAX      = +2147483647
WINT_MIN       = 0
WINT_MAX       = 4294967295

[edit] Limits of floating-point types

Defined in header <float.h>
FLT_RADIX
the radix (integer base) used by the representation of all three floating-point types
(macro constant)
DECIMAL_DIG
(C99)
conversion from long double to decimal with at least DECIMAL_DIG digits and back to long double is the identity conversion: this is the decimal precision required to serialize/deserialize a long double
(macro constant)
FLT_DECIMAL_DIGDBL_DECIMAL_DIGLDBL_DECIMAL_DIG
(C11)
conversion from float/double/long double to decimal with at least FLT_DECIMAL_DIG/DBL_DECIMAL_DIG/LDBL_DECIMAL_DIG digits and back is the identity conversion: this is the decimal precision required to serialize/deserialize a floating-point value. Defined to at least 6, 10, and 10 respectively, or 9 for IEEE float and 17 for IEEE double (see also the C++ analog: max_digits10)
(macro constant)
FLT_MINDBL_MINLDBL_MIN
minimum, normalized, positive value of float, double and long double respectively
(macro constant)
FLT_TRUE_MINDBL_TRUE_MINLDBL_TRUE_MIN
(C11)
minimum positive value of float, double and long double respectively
(macro constant)
FLT_MAXDBL_MAXLDBL_MAX
maximum finite value of float, double and long double respectively
(macro constant)
FLT_EPSILONDBL_EPSILONLDBL_EPSILON
absolute value difference between 1.0 and the next representable value for float, double and long double respectively
(macro constant)
FLT_DIGDBL_DIGLDBL_DIG
number of decimal digits that are guaranteed to be preserved in text → float/double/long double → text roundtrip without change due to rounding or overflow (see the C++ analog digits10 for detail)
(macro constant)
FLT_MANT_DIGDBL_MANT_DIGLDBL_MANT_DIG
number of base-FLT_RADIX digits that are in the floating-point mantissa and that can be represented without losing precision for float, double and long double respectively
(macro constant)
FLT_MIN_EXPDBL_MIN_EXPLDBL_MIN_EXP
minimum negative integer such that FLT_RADIX raised by power one less than that integer is a normalized float, double and long double respectively
(macro constant)
FLT_MIN_10_EXPDBL_MIN_10_EXPLDBL_MIN_10_EXP
minimum negative integer such that 10 raised to that power is a normalized float, double and long double respectively
(macro constant)
FLT_MAX_EXPDBL_MAX_EXPLDBL_MAX_EXP
maximum positive integer such that FLT_RADIX raised by power one less than that integer is a representable finite float, double and long double respectively
(macro constant)
FLT_MAX_10_EXPDBL_MAX_10_EXPLDBL_MAX_10_EXP
maximum positive integer such that 10 raised to that power is a representable finite float, double and long double respectively
(macro constant)
rounding mode of floating-point arithmetic
(macro constant)
use of extended precision for intermediate results:
0 – not used, 1double is used instead of float, 2long double is used
(macro constant)
FLT_HAS_SUBNORMDBL_HAS_SUBNORMLDBL_HAS_SUBNORM
(C11)(deprecated in C23)
whether the type supports subnormal (denormal) numbers:
-1 – indeterminable, 0 – absent, 1 – present
(macro constant)

[edit] Example

#include <float.h>
#include <math.h>
#include <stdio.h>
 
int main(void)
{
    printf("DECIMAL_DIG     = %d\n", DECIMAL_DIG);
    printf("FLT_DECIMAL_DIG = %d\n", FLT_DECIMAL_DIG);
    printf("FLT_RADIX       = %d\n", FLT_RADIX);
    printf("FLT_MIN         = %e\n", FLT_MIN);
    printf("FLT_MAX         = %e\n", FLT_MAX);
    printf("FLT_EPSILON     = %e\n", FLT_EPSILON);
    printf("FLT_DIG         = %d\n", FLT_DIG);
    printf("FLT_MANT_DIG    = %d\n", FLT_MANT_DIG);
    printf("FLT_MIN_EXP     = %d\n", FLT_MIN_EXP);
    printf("FLT_MIN_10_EXP  = %d\n", FLT_MIN_10_EXP);
    printf("FLT_MAX_EXP     = %d\n", FLT_MAX_EXP);
    printf("FLT_MAX_10_EXP  = %d\n", FLT_MAX_10_EXP);
    printf("FLT_ROUNDS      = %d\n", FLT_ROUNDS);
    printf("FLT_EVAL_METHOD = %d\n", FLT_EVAL_METHOD);
    printf("FLT_HAS_SUBNORM = %d\n", FLT_HAS_SUBNORM);
}

Possible output:

DECIMAL_DIG     = 37
FLT_DECIMAL_DIG = 9
FLT_RADIX       = 2
FLT_MIN         = 1.175494e-38
FLT_MAX         = 3.402823e+38
FLT_EPSILON     = 1.192093e-07
FLT_DIG         = 6
FLT_MANT_DIG    = 24
FLT_MIN_EXP     = -125
FLT_MIN_10_EXP  = -37
FLT_MAX_EXP     = 128
FLT_MAX_10_EXP  = 38
FLT_ROUNDS      = 1
FLT_EVAL_METHOD = 1
FLT_HAS_SUBNORM = 1

[edit] References

  • C23 standard (ISO/IEC 9899:2024):
  • 5.2.4.2 Numerical limits (p: TBD)
  • 7.22.3 Limits of other integer types (p: TBD)
  • C17 standard (ISO/IEC 9899:2018):
  • 5.2.4.2 Numerical limits (p: 20-27)
  • 7.20.3 Limits of other integer types (p: 215-216)
  • C11 standard (ISO/IEC 9899:2011):
  • 5.2.4.2 Numerical limits (p: 26-34)
  • 7.20.3 Limits of other integer types (p: 293-294)
  • C99 standard (ISO/IEC 9899:1999):
  • 5.2.4.2 Numerical limits (p: 21-28)
  • 7.18.3 Limits of other integer types (p: 259-260)
  • C89/C90 standard (ISO/IEC 9899:1990):
  • 2.2.4.2 Numerical limits

[edit] See also

C++ documentation for C numeric limits interface