(See also
for type system overview and
the list of type-related utilities
that are provided by the C++ library)
The following types are collectively called fundamental types :
(possibly cv-qualified) void
void
void — type with an empty set of values. It is an
that cannot be completed (consequently, objects of type void are disallowed). There are no
of void, nor
to void. However,
and
returning type void (procedures in other languages) are permitted.std::nullptr_t
names the type of the null pointer literal,
. It is a distinct type that is not itself a pointer type or a pointer to member type. All its prvalues are
. sizeof(std::nullptr_t) is equal to sizeof(void*).
The name std::nullptr_t is declared in
.
(since C++11)std::meta::info
std::meta::info names the type of reflection values. There exists a unique null reflection. Every other reflection represents a language construct.
The name std::meta::info is declared in
.
(since C++26)Integral types
Standard integer types
int — basic integer type. The keyword int may be omitted if any of the modifiers listed below are used. If no length modifiers are present, it's guaranteed to have a width of at least 16 bits. However, on 32/64 bit systems it is almost exclusively guaranteed to have width of at least 32 bits (see below).ModifiersModifies the basic integer type. Can be mixed in any order. Only one of each group can be present in type name.
Signedness:
signed — target type will have signed representation (this is the default if omitted)unsigned — target type will have unsigned representationSize:
short — target type will be optimized for space and will have width of at least 16 bits.long — target type will have width of at least 32 bits.long long — target type will have width of at least 64 bits.(since C++11)Note: as with all type specifiers, any order is permitted: unsignedlonglongint and longintunsignedlong name the same type.
PropertiesThe following table summarizes all available standard integer types and their properties in various common data models:
Type specifier Equivalent type Width in bits by
C++ standard LP32 ILP32 LLP64 LP64 signedchar
signedcharat least
88888unsignedchar
unsignedcharshort
shortintat least
1616161616shortint
signedshort
signedshortint
unsignedshort
unsignedshortintunsignedshortint
int
intat least
1616323232signed
signedint
unsigned
unsignedintunsignedint
long
longintat least
3232323264longint
signedlong
signedlongint
unsignedlong
unsignedlongintunsignedlongint
longlong
longlongint
(C++11)at least
6464646464longlongint
signedlonglong
signedlonglongint
unsignedlonglong
unsignedlonglongint
(C++11)unsignedlonglongint
Note: integer arithmetic is defined differently for the signed and unsigned integer types. See
, in particular
.
is the unsigned integer type of the result of the
operator as well as the
operator and the
operator(since C++11).
Extended integer types
The extended integer types are implementation-defined. Note that
are typically aliases of the standard integer types.
(since C++11)Boolean type
bool — integer type, capable of holding one of the two values:
or
. The value of sizeof(bool) is implementation defined and might differ from 1.Character types
Character types are integer types used for a character representation.
signed char — type for signed character representation.unsigned char — type for unsigned character representation. Also used to inspect
(raw memory).char — type for character representation which can be most efficiently processed on the target system (has the same representation and alignment as either signed char or unsigned char, but is always a distinct type).
use this type to represent code units. For every value of type unsigned char in range [0, 255], converting the value to char and then back to unsigned char produces the original value.(since C++11) The signedness of char depends on the compiler and the target platform: the defaults for ARM and PowerPC are typically unsigned, the defaults for x86 and x64 are typically signed.wchar_t — type for wide character representation (see
). It has the same size, signedness, and alignment as one of the integer types, but is a distinct type. In practice, it is 32 bits and holds UTF-32 on Linux and many other non-Windows systems, but 16 bits and holds UTF-16 code units on Windows. The standard used to require wchar_t to be large enough to represent any supported character code point. However, such requirement cannot be fulfilled on Windows, and thus it is considered as a
and removed.char16_t — type for UTF-16 character representation, required to be large enough to represent any UTF-16 code unit (16 bits). It has the same size, signedness, and alignment as
, but is a distinct type.char32_t — type for UTF-32 character representation, required to be large enough to represent any UTF-32 code unit (32 bits). It has the same size, signedness, and alignment as
, but is a distinct type.(since C++11)char8_t — type for UTF-8 character representation, required to be large enough to represent any UTF-8 code unit (8 bits). It has the same size, signedness, and alignment as unsigned char (and therefore, the same size and alignment as char and signed char), but is a distinct type.(since C++20)Besides the minimal bit counts, the C++ Standard guarantees that
1 == sizeof(char) ≤ sizeof(short) ≤ sizeof(int) ≤ sizeof(long) ≤ sizeof(longlong).Note: this allows the extreme case in which
are sized 64 bits, all types (including char) are 64 bits wide, and
returns 1 for every type.
Floating-point types
Standard floating-point types
The following three types and their cv-qualified versions are collectively called standard floating-point types.
float — single precision floating-point type. Usually
.double — double precision floating-point type. Usually
.long double — extended precision floating-point type. Does not necessarily map to types mandated by IEEE-754.
is used by some HP-UX, SPARC, MIPS, ARM64, and z/OS implementations.
The most well known
IEEE-754 binary64-extended format
is
x87 80-bit extended precision format
. It is used by many x86 and x86-64 implementations (a notable exception is MSVC, which implements long double in the same format as double, i.e. binary64).
On PowerPC
can be used.
Properties
Floating-point types may support
:
infinity (positive and negative), see
the negative zero, -0.0. It compares equal to the positive zero, but is meaningful in some arithmetic operations, e.g. 1.0/0.0==INFINITY, but 1.0/-0.0==-INFINITY), and for some mathematical functions, e.g.
not-a-number (NaN), which does not compare equal with anything (including itself). Multiple bit patterns represent NaNs, see
,
. Note that C++ takes no special notice of signalling NaNs other than detecting their support by
std::numeric_limits::has_signaling_NaN
, and treats all NaNs as quiet.
Floating-point numbers may be used with
+, -, /, and * as well as various mathematical functions from
. Both built-in operators and library functions may raise floating-point exceptions and set
as described in
.
Floating-point expressions may have greater range and precision than indicated by their types, see
. Floating-point expressions may also be contracted, that is, calculated as if all intermediate values have infinite range and precision, see
. Standard C++ does not restrict the accuracy of floating-point operations.
Some operations on floating-point numbers are affected by and modify the state of
the floating-point environment
(most notably, the rounding direction).
are defined between floating types and integer types.
See
limits of floating-point types
and
for additional details, limits, and properties of the floating-point types.
Range of values
The following table provides a reference for the limits of common numeric representations.
Prior to C++20, the C++ Standard allowed any signed integer representation, and the minimum guaranteed range of N-bit signed integers was from -(2N-1
-1) to +2N-1
-1 (e.g. −127 to 127 for a signed 8-bit type), which corresponds to the limits of
or
.
However, all C++ compilers use
representation, and as of C++20, it is the only representation allowed by the standard, with the guaranteed range from -2N-1
to +2N-1
-1 (e.g. −128 to 127 for a signed 8-bit type).
8-bit ones' complement and sign-and-magnitude representations for char have been disallowed since C++11 (via the resolution of
), because a UTF-8 code unit of value 0x80 used in a
must be storable in a char type object.
The range for a floating-point type T is defined as follows:
The minimum guaranteed range is the most negative finite floating-point number representable in T through the most positive finite floating-point number representable in T.
If negative infinity is representable in T, the range of T is extended to all negative real numbers.
If positive infinity is representable in T, the range of T is extended to all positive real numbers.
Since negative and positive infinity are representable in
formats, all real numbers lie within the range of representable values of a floating-point type adhering to ISO/IEC/IEEE 60559.
Type Size in bits Format Value range Approximate Exact character 8 signed −128 to 127unsigned 0 to 25516 UTF-16 0 to 6553532 UTF-32 0 to 1114111 (0x10ffff) integer 16 signed ± 3.27 · 104−32768 to 32767unsigned 0 to 6.55 · 1040 to 6553532 signed ± 2.14 · 109−2,147,483,648 to 2,147,483,647unsigned 0 to 4.29 · 1090 to 4,294,967,29564 signed ± 9.22 · 1018−9,223,372,036,854,775,808 to 9,223,372,036,854,775,807unsigned 0 to 1.84 · 10190 to 18,446,744,073,709,551,615binary
floating-
point 32
min subnormal:
± 1.401,298,4 · 10−45
min normal:
± 1.175,494,3 · 10−38
max:
± 3.402,823,4 · 1038
min subnormal:
±0x1p−149
min normal:
±0x1p−126
max:
±0x1.fffffep+127
64
min subnormal:
± 4.940,656,458,412 · 10−324
min normal:
± 2.225,073,858,507,201,4 · 10− 308
max:
± 1.797,693,134,862,315,7 · 10308
min subnormal:
±0x1p−1074
min normal:
±0x1p−1022
max:
±0x1.fffffffffffffp+1023
80
min subnormal:
± 3.645,199,531,882,474,602,528
· 10−4951
min normal:
± 3.362,103,143,112,093,506,263
· 10−4932
max:
± 1.189,731,495,357,231,765,021
· 104932
min subnormal:
±0x1p−16445
min normal:
±0x1p−16382
max:
±0x1.fffffffffffffffep+16383
128
min subnormal:
± 6.475,175,119,438,025,110,924,
438,958,227,646,552,5 · 10−4966
min normal:
± 3.362,103,143,112,093,506,262,
677,817,321,752,602,6 · 10−4932
max:
± 1.189,731,495,357,231,765,085,
759,326,628,007,016,2 · 104932
min subnormal:
±0x1p−16494
min normal:
±0x1p−16382
max:
±0x1.ffffffffffffffffffffffffffff
p+16383
The object representation usually occupies 96/128 bits on 32/64-bit platforms respectively.
Note: actual (as opposed to guaranteed minimal) limits on the values representable by these types are available in
and
.
Data models
The choices made by each implementation about the sizes of the fundamental types are collectively known as data model. Four data models found wide acceptance:
32 bit systems:
LP32 or 2/4/4 (int is 16-bit, long and pointer are 32-bit)
Win16 API
ILP32 or 4/4/4 (int, long, and pointer are 32-bit);
Win32 API
Unix and Unix-like systems (Linux, macOS)
64 bit systems:
LLP64 or 4/4/8 (int and long are 32-bit, pointer is 64-bit)
(also called the Windows API) with compilation target
(AArch64) or
(a.k.a. x64)
LP64 or 4/8/8 (int is 32-bit, long and pointer are 64-bit)
Unix and Unix-like systems (Linux, macOS)
Other models are very rare. For example, ILP64 (8/8/8: int, long, and pointer are 64-bit) only appeared in some early 64-bit Unix systems (e.g.
).
Notes
Feature-test macro ValueStdFeature
(C++11)New character types (char16_t and char32_t)
(C++20)char8_t
(C++23)char8_t compatibility and portability fix (
allow initialization of (unsigned) char arrays
from
) Keywords
,
,
,
,
,
,
,
,
,
,
,
,
,
,
,
Defect 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 the constraints placed on a floating-point implementation was unspecified specified as
no constraint
C++11 char is not guaranteed to be able to represent UTF-8 code unit 0x80 guaranteed
C++11 cv-qualified
was not a fundemental type it is
C++98 the ranges of representable values for floating-point types were not specified specified
C++98 wchar_t was required to be able to represent distinct codes for all members
of the largest extended character set specified among the supported locales not required References
C++23 standard (ISO/IEC 14882:2024):
6.8.2 Fundamental types [basic.fundamental]
C++20 standard (ISO/IEC 14882:2020):
6.8.1 Fundamental types [basic.fundamental]
C++17 standard (ISO/IEC 14882:2017):
6.9.1 Fundamental types [basic.fundamental]
C++14 standard (ISO/IEC 14882:2014):
3.9.1 Fundamental types [basic.fundamental]
C++11 standard (ISO/IEC 14882:2011):
3.9.1 Fundamental types [basic.fundamental]
C++03 standard (ISO/IEC 14882:2003):
3.9.1 Fundamental types [basic.fundamental]
C++98 standard (ISO/IEC 14882:1998):
3.9.1 Fundamental types [basic.fundamental]
See also