Fundamental types

< cpp‎ | language
Revision as of 09:02, 14 December 2012 by Cubbi (Talk | contribs)

C++ language
General topics
Flow control
Conditional execution statements
Iteration statements
Jump statements
function declaration
lambda function declaration
function template
inline specifier
exception specifications (deprecated)
noexcept specifier (C++11)
decltype specifier (C++11)
cv specifiers
storage duration specifiers
constexpr specifier (C++11)
auto specifier (C++11)
alignas specifier (C++11)
alternative representations
typedef declaration
type alias declaration (C++11)
attributes (C++11)
implicit conversions
const_cast conversion
static_cast conversion
dynamic_cast conversion
reinterpret_cast conversion
C-style and functional cast
Memory allocation
Class-specific function properties
Special member functions
class template
function template
template specialization
parameter packs (C++11)
Inline assembly

(Also see the list of type-related utilities that are provided by C++.)


Boolean type

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

Character types

signed char - type for signed character representation.
unsigned char - type for unsigned character representation.
char - type for character representation which can be most efficiently processed on the target system (equivalent to either signed char or unsigned char).
wchar_t - type for wide character representation
char16_t - type for UTF-16 character representation (since C++11)
char32_t - type for UTF-32 character representation (since C++11)

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).


Modifies the integer type. Can be mixed in any order. Only one of each group can be present in type definition.


signed - target type will have signed representation (this is the default if omitted)
unsigned - target type will have unsigned representation


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)


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 int at least
16 16 16 16
short int
signed short
signed short int
unsigned short
unsigned short int
unsigned short int
int at least
16 32 32 32
signed int
unsigned int
unsigned int
long int at least
32 32 32 64
long int
signed long
signed long int
unsigned long
unsigned long int
unsigned long int
long long
long long int
at least
64 64 64 64
long long int
signed long long
signed long long int
unsigned long long
unsigned long long int
unsigned long long int

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, as an extreme case, an implementation where all types, including char, are 64 bits wide, and sizeof returns 1 for every type.

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).

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.

Range of values

The following table provides a reference for limits of common numeric representations. Note, that all popular data models (including all of ILP32, LP32, LP64, LLP64) use two's complement arithmetic. Also, the C++ Standard does not specify which arithmetic would be used, thus it guarantees only the limits of one's complement arithmetic.

Type Size in bits Format Value range
Approximate Exact
character 8 signed (one's complement) -127 to 127
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) -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) -2,147,483,648 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) -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
unsigned 0 to 1.84 · 1019 0 to 18,446,744,073,709,551,615
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
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


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

See also