(See also type for type system overview and the list of typerelated 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.
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.
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 256 different values (in order to be suitable for storing UTF8 encoded data) (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 UTF16 code units) It has the same size, signedness, and alignment as one of the integral types, but is a distinct type.
 char16_t  type for UTF16 character representation, required to be large enough to represent any UTF16 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 UTF32 character representation, required to be large enough to represent any UTF32 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) 
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

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.
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)

 ILP32 or 4/4/4 (int, long, and pointer are 32bit);
 Win32 API
 Unix and Unixlike systems (Linux, Mac OS X)
64 bit systems:
 LLP64 or 4/4/8 (int and long are 32bit, pointer is 64bit)

 LP64 or 4/8/8 (int is 32bit, long and pointer are 64bit)
 Unix and Unixlike systems (Linux, Mac OS X)
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).
Floating point types
 float  single precision floating point type. Usually IEEE754 32 bit floating point type
 double  double precision floating point type. Usually IEEE754 64 bit floating point type
 long double  extended precision floating point type. Does not necessarily map to types mandated by IEEE754. Usually 80bit x87 floating point type on x86 and x8664 architectures.
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.
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.
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 floating point types and std::numeric_limits for additional details, limits, and properties of the floatingpoint types.
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 signandmagnitude) 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

Approximate

Exact

character

8

signed (one's complement)

127 to 127^{[note 1]}

signed (two's complement)

128 to 127

unsigned

0 to 255

16

unsigned

0 to 65535

32

unsigned

0 to 1114111 (0x10ffff)

integral

16

signed (one's complement)

± 3.27 · 10^{4}

32767 to 32767

signed (two's complement)

32768 to 32767

unsigned

0 to 6.55 · 10^{4}

0 to 65535

32

signed (one's complement)

± 2.14 · 10^{9}

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 · 10^{9}

0 to 4,294,967,295

64

signed (one's complement)

± 9.22 · 10^{18}

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 · 10^{19}

0 to 18,446,744,073,709,551,615

floating point

32

IEEE754

± 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 · 10^{38}

64

IEEE754

± 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 · 10^{308}

 ↑ As of C++14, char must represent 256 distinct values, bijectively convertible to the values 0..255 of unsigned char, which may require a wider range of values.
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
bool,
true,
false,
char,
wchar_t,
char16_t,
char32_t,
int,
short,
long,
signed,
unsigned,
float,
double
See also