Fundamental types
(See also type for type system overview and the list of typerelated utilities that are provided by the C++ library)
Contents 
[edit] Void type
 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.
[edit] std::nullptr_t (since C++11)
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*).
[edit] 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 16bit, long and pointer are 32bit)
 Win16 API
 ILP32 or 4/4/4 (int, long, and pointer are 32bit);
 Win32 API
 Unix and Unixlike systems (Linux, macOS)
64 bit systems:
 LLP64 or 4/4/8 (int and long are 32bit, pointer is 64bit)
 Win32 API (also called the Windows API) with compilation target 64bit ARM (AArch64) or x8664 (a.k.a. x64)
 LP64 or 4/8/8 (int is 32bit, long and pointer are 64bit)
 Unix and Unixlike systems (Linux, macOS)
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).
[edit] Integral types
[edit] 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).
[edit] Modifiers
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.
[edit] Properties
The following table summarizes all available standard 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  
signed char

signed char  at least 8 
8  8  8  8 
unsigned char

unsigned char  
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).
[edit] Extended integer types (since C++11)
The extended integer types are implementationdefined. Note that fixed width integer types are typically aliases of the standard integer types.
[edit] Boolean type
 bool — integer type, capable of holding one of the two values:
true
orfalse
. The value of sizeof(bool) is implementation defined and might differ from 1.
[edit] 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 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.

(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.
[edit] Floatingpoint types
[edit] Standard floatingpoint types
The following three types and their cvqualified versions are collectively called standard floatingpoint types.
 float — single precision floatingpoint type. Usually IEEE754 binary32 format.
 double — double precision floatingpoint type. Usually IEEE754 binary64 format.
 long double — extended precision floatingpoint type. Does not necessarily map to types mandated by IEEE754.
 IEEE754 binary128 format is used by some HPUX, SPARC, MIPS, ARM64, and z/OS implementations.
 The most well known IEEE754 binary64extended format is x87 80bit extended precision format. It is used by many x86 and x8664 implementations (a notable exception is MSVC, which implements long double in the same format as double, i.e. binary64).
 On PowerPC doubledouble can be used.
[edit] Extended floatingpoint types (since C++23)
The extended floatingpoint types are implementationdefined. They may include fixed width floatingpoint types.
[edit] Properties
Floatingpoint types may support special values:
 infinity (positive and negative), see INFINITY
 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. sqrt(std::complex)
 notanumber (NaN), which does not compare equal with anything (including itself). Multiple bit patterns represent NaNs, see 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.
Floatingpoint numbers may be used with arithmetic operators +, , /, and * as well as 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 floating types and integer types.
See Limits of floatingpoint types and std::numeric_limits for additional details, limits, and properties of the floatingpoint types.
[edit] 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 Nbit signed integers was from (2N1
1) to +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 2N1
to +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 the resolution of CWG issue 1759), because a UTF8 code unit of value 0x80 used in a UTF8 string literal must be storable in a char type object.
The range for a floatingpoint type T
is defined as follows:
 The minimum guaranteed range is the most negative finite floatingpoint number representable in
T
through the most positive finite floatingpoint number representable inT
.  If negative infinity is representable in
T
, the range ofT
is extended to all negative real numbers.  If positive infinity is representable in
T
, the range ofT
is extended to all positive real numbers.
Since negative and positive infinity are representable in ISO/IEC/IEEE 60559 formats, all real numbers lie within the range of representable values of a floatingpoint type adhering to ISO/IEC/IEEE 60559.
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 


 ↑ The object representation usually occupies 96/128 bits on 32/64bit platforms respectively.
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.
[edit] Notes
Featuretest macro  Value  Std  Feature 

__cpp_unicode_characters 
200704L  (C++11)  New character types (char16_t and char32_t) 
__cpp_char8_t 
201811L  (C++20)  char8_t 
202207L  (C++23)  char8_t compatibility and portability fix (allow initialization of (unsigned) char arrays from UTF8 string literals)

[edit] Keywords
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.
[edit] Defect reports
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 
CWG 2723  C++98  the ranges of representable values for floatingpoint types were not specified  specified 
P2460R2  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 
[edit] References
 C++23 standard (ISO/IEC 14882:2023):
 6.8.2.11 Fundamental types [basic.fundamental]
 C++20 standard (ISO/IEC 14882:2020):
 TBD Fundamental types [basic.fundamental]
 C++17 standard (ISO/IEC 14882:2017):
 TBD Fundamental types [basic.fundamental]
 C++14 standard (ISO/IEC 14882:2014):
 TBD Fundamental types [basic.fundamental]
 C++11 standard (ISO/IEC 14882:2011):
 TBD Fundamental types [basic.fundamental]
 C++98 standard (ISO/IEC 14882:1998):
 TBD Fundamental types [basic.fundamental]
[edit] See also
 The C++ type system overview
 Constvolatility (cv) specifiers and qualifiers
 Storage duration specifiers
C documentation for arithmetic types
