See also
interface.
Characteristics of integer types
Characteristics of core language integer types Defined in header
BOOL_WIDTH
(C++26)
bit width of bool
(macro constant)
CHAR_BIT
bit width of byte
(macro constant)
MB_LEN_MAX
maximum number of bytes in a multibyte character
(macro constant)
CHAR_WIDTH
(C++26)
bit width of char
(macro constant)
CHAR_MIN
minimum value of char
(macro constant)
CHAR_MAX
maximum value of char
(macro constant)
SCHAR_WIDTHSHRT_WIDTHINT_WIDTHLONG_WIDTHLLONG_WIDTH
(C++26)(C++26)(C++26)(C++26)(C++26)
bit width of signedchar, short, int, long, and longlong respectively
(macro constant)
SCHAR_MINSHRT_MININT_MINLONG_MINLLONG_MIN
(C++11)
minimum value of signedchar, short, int, long and longlong respectively
(macro constant)
SCHAR_MAXSHRT_MAXINT_MAXLONG_MAXLLONG_MAX
(C++11)
maximum value of signedchar, short, int, long and longlong respectively
(macro constant)
UCHAR_WIDTHUSHRT_WIDTHUINT_WIDTHULONG_WIDTHULLONG_WIDTH
(C++26)(C++26)(C++26)(C++26)(C++26)
bit width of unsignedchar, unsignedshort, unsignedint, unsignedlong, and unsignedlonglong respectively
(macro constant)
UCHAR_MAXUSHRT_MAXUINT_MAXULONG_MAXULLONG_MAX
(C++11)
maximum value of unsignedchar, unsignedshort, unsignedint,
unsignedlong and unsignedlonglong respectively
(macro constant)
Defined in header
Defined in header
WCHAR_WIDTH
(C++26)
bit width of wchar_t
(macro constant)
WCHAR_MIN
(C++11)
minimum value of wchar_t
(macro constant)
WCHAR_MAX
(C++11)
maximum value of wchar_t
(macro constant)
Characteristics of library type aliases Defined in header
PTRDIFF_WIDTH
(C++26)
bit width of
(macro constant)
PTRDIFF_MIN
(C++11)
minimum value of
(macro constant)
PTRDIFF_MAX
(C++11)
maximum value of
(macro constant)
SIZE_WIDTH
(C++26)
bit width of
(macro constant)
SIZE_MAX
(C++11)
maximum value of
(macro constant)
SIG_ATOMIC_WIDTH
(C++26)
bit width of
(macro constant)
SIG_ATOMIC_MIN
(C++11)
minimum value of
(macro constant)
SIG_ATOMIC_MAX
(C++11)
maximum value of
(macro constant)
WINT_WIDTH
(C++26)
bit width of
(macro constant)
WINT_MIN
(C++11)
minimum value of
(macro constant)
WINT_MAX
(C++11)
maximum value of
(macro constant)
Value requirements
BOOL_WIDTH always expands to 1.
(since C++26)Each of the *_WIDTH macros (other than BOOL_WIDTH),(since C++26)CHAR_BIT and MB_LEN_MAX expands to an implementation-defined value. The allowed minimum values are listed below, where each group of macros separated by / always expand to the same value:
at least 1: MB_LEN_MAX
at least 8: CHAR_BIT / CHAR_WIDTH / SCHAR_WIDTH / UCHAR_WIDTH, WCHAR_WIDTH, SIG_ATOMIC_WIDTH
at least 16: SHRT_WIDTH / USHRT_WIDTH, INT_WIDTH / UINT_WIDTH, PTRDIFF_WIDTH, SIZE_WIDTH, WINT_WIDTH
at least 32: LONG_WIDTH / ULONG_WIDTH
at least 64: LLONG_WIDTH / ULLONG_WIDTH
Notes
The types of these constants, other than the *_WIDTH macros, (since C++26)CHAR_BIT and MB_LEN_MAX, are required to match the results of the
as applied to objects of the types they describe: CHAR_MAX may have type int or unsignedint, but never char. Similarly USHRT_MAX may not be of an unsigned type: its type may be int.
A
implementation may lack
and/or
typedef names, in which case the SIG_ATOMIC_* and/or WINT_* macros are correspondingly absent.
Example
Run this code
#include<climits>#include<cstdint>#include<iomanip>#include<iostream>#include<locale>intmain(){constexprintw=14;(std::cout<<std::left).imbue(std::locale("en_US.UTF-8"));# define COUT(x) std::cout << std::setw(w) << #x << " = " << x << '\n'COUT(BOOL_WIDTH);COUT(CHAR_BIT);COUT(CHAR_MAX);COUT(CHAR_MIN);COUT(CHAR_WIDTH);COUT(INT_MAX);COUT(INT_MIN);COUT(INT_WIDTH);COUT(LLONG_MAX);COUT(LLONG_MIN);COUT(LLONG_WIDTH);COUT(LONG_MAX);COUT(LONG_MIN);COUT(LONG_WIDTH);COUT(MB_LEN_MAX);COUT(PTRDIFF_MAX);COUT(PTRDIFF_MIN);COUT(SCHAR_MAX);COUT(SCHAR_MIN);COUT(SCHAR_WIDTH);COUT(SHRT_MAX);COUT(SHRT_MIN);COUT(SHRT_WIDTH);COUT(SIG_ATOMIC_MAX);COUT(SIG_ATOMIC_MIN);COUT(SIZE_MAX);COUT(UCHAR_MAX);COUT(UCHAR_WIDTH);COUT(UINT_MAX);COUT(UINT_WIDTH);COUT(ULLONG_MAX);COUT(ULLONG_WIDTH);COUT(ULONG_MAX);COUT(ULONG_WIDTH);COUT(USHRT_MAX);COUT(USHRT_WIDTH);COUT(WCHAR_MAX);COUT(WCHAR_MIN);COUT(WINT_MAX);COUT(WINT_MIN);}Possible output:
BOOL_WIDTH = 1 CHAR_BIT = 8 CHAR_MAX = 127 CHAR_MIN = -128 CHAR_WIDTH = 8 INT_MAX = 2,147,483,647 INT_MIN = -2,147,483,648 INT_WIDTH = 32 LLONG_MAX = 9,223,372,036,854,775,807 LLONG_MIN = -9,223,372,036,854,775,808 LLONG_WIDTH = 64 LONG_MAX = 9,223,372,036,854,775,807 LONG_MIN = -9,223,372,036,854,775,808 LONG_WIDTH = 64 MB_LEN_MAX = 16 PTRDIFF_MAX = 9,223,372,036,854,775,807 PTRDIFF_MIN = -9,223,372,036,854,775,808 SCHAR_MAX = 127 SCHAR_MIN = -128 SCHAR_WIDTH = 8 SHRT_MAX = 32,767 SHRT_MIN = -32,768 SHRT_WIDTH = 16 SIG_ATOMIC_MAX = 2,147,483,647 SIG_ATOMIC_MIN = -2,147,483,648 SIZE_MAX = 18,446,744,073,709,551,615 UCHAR_MAX = 255 UCHAR_WIDTH = 8 UINT_MAX = 4,294,967,295 UINT_WIDTH = 32 ULLONG_MAX = 18,446,744,073,709,551,615 ULLONG_WIDTH = 64 ULONG_MAX = 18,446,744,073,709,551,615 ULONG_WIDTH = 64 USHRT_MAX = 65,535 USHRT_WIDTH = 16 WCHAR_MAX = 2,147,483,647 WCHAR_MIN = -2,147,483,648 WINT_MAX = 4,294,967,295 WINT_MIN = 0 Characteristics and special values of floating-point types
Characteristics of floating-point types default rounding mode of floating-point arithmetic
(macro constant)
(C++11)
specifies in what precision all arithmetic operations are done
(macro constant)
FLT_HAS_SUBNORMDBL_HAS_SUBNORMLDBL_HAS_SUBNORM
(C++17)(deprecated in C++26)
specifies whether the type supports subnormal (
) numbers:
-1 – indeterminable, 0 – absent, 1 – present
(macro constant)
FLT_RADIX
the radix (integer base) used by the representation of all three floating-point types
(macro constant)
FLT_MANT_DIGDBL_MANT_DIGLDBL_MANT_DIG
number of base FLT_RADIX digits that can be represented without losing precision for float, double and longdouble respectively
(macro constant)
FLT_DECIMAL_DIGDBL_DECIMAL_DIGLDBL_DECIMAL_DIG
(C++17)
conversion from float/double/longdouble 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
(macro constant)
DECIMAL_DIG
(C++11)(deprecated in C++26)
conversion from longdouble to decimal with at least DECIMAL_DIG digits and back to longdouble is the identity conversion: this is the decimal precision required to serialize/deserialize a longdouble
(macro constant)
FLT_DIGDBL_DIGLDBL_DIG
number of decimal digits that are guaranteed to be preserved in text → float/double/longdouble → text roundtrip without change due to rounding or overflow
(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 longdouble 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 longdouble 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)
FLT_MAXDBL_MAXLDBL_MAX
maximum finite value of float, double and long double respectively
(macro constant)
FLT_EPSILONDBL_EPSILONLDBL_EPSILON
difference between 1.0 and the next representable value for float, double and long double respectively
(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
(C++17)
minimum positive value of float, double and long double respectively
(macro constant)
Special values of floating-point types Defined in header
(deprecated in C++26)
Defined in header
(since C++26)
(C++11)
evaluates to positive infinity (if exists)
(macro constant)
(C++11)
evaluates to a quiet NaN of type float (if exists)
(macro constant)
Defined in header
(C++26)
evaluates to a signaling NaN of float, double and long double respectively (if exists)
(macro constant)
Example
Run this code
#include <cfloat> #include <iomanip> #include <iostream> int main() { int w = 16; std::cout << std::left; // std::cout << std::setprecision(53); # define COUT(x) std::cout << std::setw(w) << #x << " = " << x << '\n' COUT( FLT_RADIX ); COUT( DECIMAL_DIG ); COUT( FLT_DECIMAL_DIG ); COUT( DBL_DECIMAL_DIG ); COUT( LDBL_DECIMAL_DIG ); COUT( FLT_MIN ); COUT( DBL_MIN ); COUT( LDBL_MIN ); COUT( FLT_TRUE_MIN ); COUT( DBL_TRUE_MIN ); COUT( LDBL_TRUE_MIN ); COUT( FLT_MAX ); COUT( DBL_MAX ); COUT( LDBL_MAX ); COUT( FLT_EPSILON ); COUT( DBL_EPSILON ); COUT( LDBL_EPSILON ); COUT( FLT_DIG ); COUT( DBL_DIG ); COUT( LDBL_DIG ); COUT( FLT_MANT_DIG ); COUT( DBL_MANT_DIG ); COUT( LDBL_MANT_DIG ); COUT( FLT_MIN_EXP ); COUT( DBL_MIN_EXP ); COUT( LDBL_MIN_EXP ); COUT( FLT_MIN_10_EXP ); COUT( DBL_MIN_10_EXP ); COUT( LDBL_MIN_10_EXP ); COUT( FLT_MAX_EXP ); COUT( DBL_MAX_EXP ); COUT( LDBL_MAX_EXP ); COUT( FLT_MAX_10_EXP ); COUT( DBL_MAX_10_EXP ); COUT( LDBL_MAX_10_EXP ); COUT( FLT_ROUNDS ); COUT( FLT_EVAL_METHOD ); COUT( FLT_HAS_SUBNORM ); COUT( DBL_HAS_SUBNORM ); COUT( LDBL_HAS_SUBNORM ); }Possible output:
FLT_RADIX = 2 DECIMAL_DIG = 21 FLT_DECIMAL_DIG = 9 DBL_DECIMAL_DIG = 17 LDBL_DECIMAL_DIG = 21 FLT_MIN = 1.17549e-38 DBL_MIN = 2.22507e-308 LDBL_MIN = 3.3621e-4932 FLT_TRUE_MIN = 1.4013e-45 DBL_TRUE_MIN = 4.94066e-324 LDBL_TRUE_MIN = 3.6452e-4951 FLT_MAX = 3.40282e+38 DBL_MAX = 1.79769e+308 LDBL_MAX = 1.18973e+4932 FLT_EPSILON = 1.19209e-07 DBL_EPSILON = 2.22045e-16 LDBL_EPSILON = 1.0842e-19 FLT_DIG = 6 DBL_DIG = 15 LDBL_DIG = 18 FLT_MANT_DIG = 24 DBL_MANT_DIG = 53 LDBL_MANT_DIG = 64 FLT_MIN_EXP = -125 DBL_MIN_EXP = -1021 LDBL_MIN_EXP = -16381 FLT_MIN_10_EXP = -37 DBL_MIN_10_EXP = -307 LDBL_MIN_10_EXP = -4931 FLT_MAX_EXP = 128 DBL_MAX_EXP = 1024 LDBL_MAX_EXP = 16384 FLT_MAX_10_EXP = 38 DBL_MAX_10_EXP = 308 LDBL_MAX_10_EXP = 4932 FLT_ROUNDS = 1 FLT_EVAL_METHOD = 0 FLT_HAS_SUBNORM = 1 DBL_HAS_SUBNORM = 1 LDBL_HAS_SUBNORM = 1Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR Applied to Behavior as published Correct behavior
C++98 it was unclear whether the types of the macros in
are guaranteed
to match the type to which they refer (C++ refers to C, and C says no) clarified as not
guaranteed See also