(See also type for type system overview and the list of typerelated utilities that are provided by the C++ library).
void
 type with an empty set of values. It is an incomplete type that cannot be completed (consequently, objects of type void
are disallowed). There are no arrays of void
, nor references to void
. However, pointers to void
and functions returning type void
(procedures in other languages) are permitted. std::nullptr_t
Defined in header <cstddef>  

typedef decltype(nullptr) nullptr_t;  (since C++11) 
std::nullptr_t
is the type of the null pointer literal, nullptr
. It is a distinct type that is not itself a pointer type or a pointer to member type. Its values are null pointer constant (see NULL
), and may be implicitly converted to any pointer and pointer to member type.
sizeof(std::nullptr_t)
is equal to sizeof(void *)
.
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:
64 bit systems:
Other models are very rare. For example, ILP64 (8/8/8: int, long, and pointer are 64bit) only appeared in some early 64bit Unix systems (e.g. UNICOS on Cray).
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). Modifies 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 representation Size.
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.  (since C++11) 
Note: as with all type specifiers, any order is permitted: unsigned long long int
and long int unsigned long
name the same type.
The following table summarizes all available integer types and their properties in various common data models:
Type specifier  Equivalent type  Width in bits by data model  

C++ standard  LP32  ILP32  LLP64  LP64  
short  short int  at least 16  16  16  16  16 
short int 

signed short 

signed short int 

unsigned short  unsigned short int 

unsigned short int 

int  int  at least 16  16  32  32  32 
signed 

signed int 

unsigned  unsigned int 

unsigned int 

long  long int  at least 32  32  32  32  64 
long int 

signed long 

signed long int 

unsigned long  unsigned long int 

unsigned long int 

long long  long long int (C++11)  at least 64  64  64  64  64 
long long int 

signed long long 

signed long long int 

unsigned long long  unsigned long long int (C++11) 

unsigned long long int 
Note: integer arithmetic is defined differently for the signed and unsigned integer types. See arithmetic operators, in particular integer overflows.
std::size_t
is the unsigned integer type of the result of the sizeof
operator as well as the sizeof...
operator and the alignof
operator (since C++11).
See also Fixed width integer types.  (since C++11) 
bool
 type, capable of holding one of the two values: true
or false
. The value of sizeof(bool)
is implementation defined and might differ from 1. signed char
 type for signed character representation. unsigned char
 type for unsigned character representation. Also used to inspect object representations (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). Multibyte characters strings 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 wide strings). 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 UTF32 on Linux and many other nonWindows systems, but 16 bits and holds UTF16 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 defect and removed by P2460R2.  (since C++11) 
 (since C++20) 
Besides the minimal bit counts, the C++ Standard guarantees that 1 == sizeof(char) <= sizeof(short) <= sizeof(int) <= sizeof(long) <= sizeof(long long)
.
Note: this allows the extreme case in which bytes are sized 64 bits, all types (including char
) are 64 bits wide, and sizeof
returns 1 for every type.
The following three types and their cvqualified versions are collectively called floatingpoint types.
float
 single precision floatingpoint type. Matches IEEE754 binary32 format if supported. double
 double precision floatingpoint type. Matches IEEE754 binary64 format if supported. long double
 extended precision floatingpoint type. Matches IEEE754 binary128 format if supported, otherwise matches IEEE754 binary64extended format if supported, otherwise matches some nonIEEE754 extended floatingpoint format as long as its precision is better than binary64 and range is at least as good as binary64, otherwise matches IEEE754 binary64 format. long double
in the same format as double
, i.e. binary64). Floatingpoint types may support special values:
INFINITY
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. sqrt(std::complex)
std::nan
, NAN
. 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. Real floatingpoint numbers may be used with arithmetic operators +  / * and various mathematical functions from <cmath>
. Both builtin operators and library functions may raise floatingpoint exceptions and set errno
as described in math errhandling
.
Floatingpoint expressions may have greater range and precision than indicated by their types, see FLT_EVAL_METHOD
. Floatingpoint expressions may also be contracted, that is, calculated as if all intermediate values have infinite range and precision, see #pragma STDC FP_CONTRACT
. Standard C++ does not restrict the accuracy of floatingpoint operations.
Some operations on floatingpoint numbers are affected by and modify the state of the floatingpoint environment (most notably, the rounding direction).
Implicit conversions are defined between real floating types and integer types.
See Limits of floatingpoint types and std::numeric_limits
for additional details, limits, and properties of the floatingpoint types.
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 Nbit signed integers was from \(\scriptsize (2^{N1}1)\)(2N1
1) to \(\scriptsize +2^{N1}1\)+2N1
1 (e.g. 127 to 127 for a signed 8bit type), which corresponds to the limits of ones' complement or signandmagnitude.
However, all C++ compilers use two's complement representation, and as of C++20, it is the only representation allowed by the standard, with the guaranteed range from \(\scriptsize 2^{N1}\)2N1
to \(\scriptsize +2^{N1}1\)+2N1
1 (e.g. 128 to 127 for a signed 8bit type).
8bit ones' complement and signandmagnitude representations for char
have been disallowed since C++11 (via CWG 1759), because a UTF8 code unit of value 0x80 used in a UTF8 string literal must be storable in a char
element object.
Type  Size in bits  Format  Value range  

Approximate  Exact  
character  8  signed  128 to 127  
unsigned  0 to 255  
16  UTF16  0 to 65535  
32  UTF32  0 to 1114111 (0x10ffff)  
integer  16  signed  ± 3.27 · 10^{4}  32768 to 32767 
unsigned  0 to 6.55 · 10^{4}  0 to 65535  
32  signed  ± 2.14 · 10^{9}  2,147,483,648 to 2,147,483,647  
unsigned  0 to 4.29 · 10^{9}  0 to 4,294,967,295  
64  signed  ± 9.22 · 10^{18}  9,223,372,036,854,775,808 to 9,223,372,036,854,775,807  
unsigned  0 to 1.84 · 10^{19}  0 to 18,446,744,073,709,551,615  
binary floating point  32  IEEE754 


64  IEEE754 



80^{[note 1]}  x86 



128  IEEE754 


Note: actual (as opposed to guaranteed minimal) limits on the values representable by these types are available in C numeric limits interface and std::numeric_limits
.
void
, bool
, true
, false
, char
, wchar_t
, char8_t
, (since C++20) char16_t
, char32_t
, (since C++11) int
, short
, long
, signed
, unsigned
, float
, double
.
The following behaviorchanging defect reports were applied retroactively to previously published C++ standards.
DR  Applied to  Behavior as published  Correct behavior 

CWG 238  C++98  the constraints placed on a floatingpoint implementation was unspecified  specified as no constraint 
CWG 1759  C++11  char is not guaranteed to be able to represent UTF8 code unit 0x80  guaranteed 
C documentation for arithmetic types 
© cppreference.com
Licensed under the Creative Commons AttributionShareAlike Unported License v3.0.
https://en.cppreference.com/w/cpp/language/types