Fundamental types

(See also type for type system overview and the list of type-related 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.

[edit] std::nullptr_t

[edit] Boolean type

bool - type, capable of holding one of the two values: true or false.

[edit] 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 (equivalent to either signed char or unsigned char, but still different type). The character types are large enough to represent 256 different values (in order to be suitable for storing UTF-8 encoded data) (since C++14)

wchar_t - type for wide character representation

char16_t - type for UTF-16 character representation

char32_t - type for UTF-32 character representation

(since C++11)

[edit] Integer types

int - basic integer type. Can be omitted if any of the modifiers are present. If no length modifiers are present, guaranteed to have 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 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)

[edit] Properties

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

Type specifier	Equivalent type	Width in bits by data model
Type specifier	Equivalent type	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	unsigned short int
int	int	at least 16	16	32	32	32
signed
signed int
unsigned	unsigned int
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	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	unsigned long long int (C++11)

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.

Note: integer arithmetic is defined differently for the signed and unsigned integer types. See arithmetic operators, in particular integer overflows.

[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 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).

[edit] 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.

[edit] Range of values

The following table provides a reference for the limits of common numeric representations. As the C++ Standard allows any signed integer representation, the table gives both the minimum guaranteed requirements (which correspond to the limits of one's complement or sign-and-magnitude) and the limits of the most commonly used implementation, two's complement. All popular data models (including all of ILP32, LP32, LP64, LLP64) use two's complement representation, though.

Type	Size in bits	Format	Value range
Type	Size in bits	Format	Approximate	Exact
character	8	signed (one's complement)	-127 to 127(until C++14)
		signed (two's complement)	-128 to 127
		unsigned	0 to 255
integral	16	signed (one's complement)	± 3.27 · 10⁴	-32767 to 32767
		signed (two's complement)	± 3.27 · 10⁴	-32768 to 32767
		unsigned	0 to 6.55 · 10⁴	0 to 65535
	32	signed (one's complement)	± 2.14 · 10⁹	-2,147,483,647 to 2,147,483,647
		signed (two's complement)	± 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 (one's complement)	± 9.22 · 10¹⁸	-9,223,372,036,854,775,807 to 9,223,372,036,854,775,807
		signed (two's complement)	± 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	± 3.4 · 10^{± 38} (~7 digits)	min subnormal: ± 1.401,298,4 · 10^-47 min normal: ± 1.175,494,3 · 10^-38 max: ± 3.402,823,4 · 10³⁸
floating point	64	IEEE-754	± 1.7 · 10^{± 308} (~15 digits)	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

[edit] Keywords

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

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