# Fundamental types

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(See also type for type system overview and the list of type-related utilities that are provided by the C++ library)

### 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.

### 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.

### Boolean type

  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.

### 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).

#### Modifiers

Modifies the 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.

  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: unsigned long long int and long int unsigned long name the same type.

#### Properties

The following table summarizes all available integer types and their properties:

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)

#### 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, Mac OS X)

64 bit systems:

  - LLP64 or 4/4/8 (int and long are 32-bit, pointer is 64-bit)
    - Win64 API
  - LP64 or 4/8/8 (int is 32-bit, long and pointer are 64-bit)
    - Unix and Unix-like systems (Linux, Mac OS X)

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. Unicos on Cray).

### Character types

  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. The character types are large enough to represent any UTF-8 eight-bit code unit (since C++14). 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). Required to be large enough to represent any supported character code point (32 bits on systems that support Unicode. A notable exception is Windows, where wchar_t is 16 bits and holds UTF-16 code units) It has the same size, signedness, and alignment as one of the integer types, but is a distinct type.

  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 std::uint_least16_t, 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 std::uint_least32_t, 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(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.

### Floating point types

  float - single precision floating point type. Usually IEEE-754 32 bit floating point type

  double - double precision floating point type. Usually IEEE-754 64 bit floating point type

  long double - extended precision floating point type. Does not necessarily map to types mandated by IEEE-754. Usually 80-bit x87 floating point type on x86 and x86-64 architectures.

#### Properties

Floating-point 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)`
- not-a-number (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.

Real floating-point numbers may be used with arithmetic operators + - / * and various mathematical functions from cmath. Both built-in operators and library functions may raise floating-point exceptions and set errno as described in `math_errhandling`

Floating-point expressions may have greater range and precision than indicated by their types, see FLT_EVAL_METHOD. Floating-point expressions may also be contracted, that is, calculated as if all intermediate values have infinite range and precision, see #pragma STDC FP_CONTRACT.

Some operations on floating-point numbers are affected by and modify the state of the floating-point environment (most notably, the rounding direction)

Implicit conversions are defined between real floating types and integer types.

See Limits of floating point types and std::numeric_limits 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 one's complement or sign-and-magnitude.

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 -2N-1
to +2N-1
-1 (e.g. -128 to 127 for a signed 8-bit type).

Type | Size in bits | Format | Value range
--- | --- | --- | ---
Approximate | Exact
character | 8 | signed |  | -128 to 127
unsigned |  | 0 to 255
16 | unsigned |  | 0 to 65535
32 | unsigned |  | 0 to 1114111 (0x10ffff)
integer | 16 | signed | ± 3.27 · 104 | -32768 to 32767
unsigned | 0 to 6.55 · 104 | 0 to 65535
32 | signed | ± 2.14 · 109 | -2,147,483,648 to 2,147,483,647
unsigned | 0 to 4.29 · 109 | 0 to 4,294,967,295
64 | signed | ± 9.22 · 1018 | -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
unsigned | 0 to 1.84 · 1019 | 0 to 18,446,744,073,709,551,615

floating
point

32

IEEE-754

- 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

IEEE-754

- 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

Note: actual (as opposed to guaranteed minimal) limits on the values representable by these types are available in <climits>, <cfloat> and std::numeric_limits

### Keywords

`void`, `bool`, `true`, `false`, `char`, `wchar_t`, `char8_t`, `char16_t`, `char32_t`, `int`, `short`, `long`, `signed`, `unsigned`, `float`, `double`

### See also

- the C++ type system overview
- const-volatility (cv) specifiers and qualifiers
- storage duration specifiers

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