# C numeric limits interface

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See also std::numeric_limits interface.

Defined in header `<cstdint>`
PTRDIFF_MIN (C++11) | minimum value of object of std::ptrdiff_t type (macro constant)
PTRDIFF_MAX (C++11) | maximum value of object of std::ptrdiff_t type (macro constant)
SIZE_MAX (C++11) | maximum value of object of std::size_t type (macro constant)
SIG_ATOMIC_MIN (C++11) | minimum value of object of std::sig_atomic_t type (macro constant)
SIG_ATOMIC_MAX (C++11) | maximum value of object of std::sig_atomic_t type (macro constant)
WCHAR_MIN (C++11) | minimum value of object of wchar_t type (macro constant)
WCHAR_MAX (C++11) | maximum value of object of wchar_t type (macro constant)
WINT_MIN (C++11) | minimum value of object of std::wint_t type (macro constant)
WINT_MAX (C++11) | maximum value of object of std::wint_t type (macro constant)

### Limits of integer types

Defined in header `<climits>`
CHAR_BIT | number of bits in a byte (macro constant)
MB_LEN_MAX | maximum number of bytes in a multibyte character (macro constant)
CHAR_MIN | minimum value of char (macro constant)
CHAR_MAX | maximum value of char (macro constant)
SCHAR_MIN SHRT_MIN INT_MIN LONG_MIN LLONG_MIN (C++11) | minimum value of signed char, short, int, long and long long respectively (macro constant)
SCHAR_MAX SHRT_MAX INT_MAX LONG_MAX LLONG_MAX (C++11) | maximum value of signed char, short, int, long and long long respectively (macro constant)
UCHAR_MAX USHRT_MAX UINT_MAX ULONG_MAX ULLONG_MAX (C++11) | maximum value of unsigned char, unsigned short, unsigned int, unsigned long and unsigned long long respectively (macro constant)

Note: 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.

### Limits of floating point types

Defined in header `<cfloat>`
FLT_RADIX | the radix (integer base) used by the representation of all three floating-point types (macro constant)
DECIMAL_DIG (C++11) | 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 (see also std::numeric_limits::max_digits10) (macro constant)

FLT_DECIMAL_DIG DBL_DECIMAL_DIG LDBL_DECIMAL_DIG
(C++17)

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 (see also std::numeric_limits::max_digits10). Defined to at least 6, 10, and 10 respectively, or 9 for IEEE float and 17 for IEEE double.
(macro constant)

FLT_MIN DBL_MIN LDBL_MIN | minimum normalized positive value of float, double and long double respectively (macro constant)
FLT_TRUE_MIN DBL_TRUE_MIN LDBL_TRUE_MIN (C++17) | minimum positive value of float, double and long double respectively (macro constant)
FLT_MAX DBL_MAX LDBL_MAX | maximum value of float, double and long double respectively (macro constant)
FLT_EPSILON DBL_EPSILON LDBL_EPSILON | difference between 1.0 and the next representable value for float, double and long double respectively (macro constant)
FLT_DIG DBL_DIG LDBL_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 std::numeric_limits::digits10 for explanation) (macro constant)
FLT_MANT_DIG DBL_MANT_DIG LDBL_MANT_DIG | number of base `FLT_RADIX` digits that can be represented without losing precision for float, double and long double respectively (macro constant)
FLT_MIN_EXP DBL_MIN_EXP LDBL_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_EXP DBL_MIN_10_EXP LDBL_MIN_10_EXP | minimum negative integer such that 10 raised by power one less than that integer is a normalized float, double and long double respectively (macro constant)
FLT_MAX_EXP DBL_MAX_EXP LDBL_MAX_EXP | maximum positive integer such that `FLT_RADIX` raised by power one more than that integer is a normalized float, double and long double respectively (macro constant)
FLT_MAX_10_EXP DBL_MAX_10_EXP LDBL_MAX_10_EXP | maximum positive integer such that 10 raised by power one more than that integer is a normalized float, double and long double respectively (macro constant)
FLT_ROUNDS | default rounding mode of floating-point arithmetics (macro constant)
FLT_EVAL_METHOD (C++11) | specifies in what precision all arithmetic operations are done (macro constant)
FLT_HAS_SUBNORM DBL_HAS_SUBNORM LDBL_HAS_SUBNORM (C++17) | specifies whether the type supports subnormal (denormal) numbers: -1 indeterminable, 0 absent, 1 present (macro constant)

### See also

- Fixed width integer types
- Arithmetic types
- C++ type system overview
- Type support (basic types, RTTI, type traits)

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