Fundamental types
 |
Questa pagina è stata tradotta in modo automatico dalla versione in ineglese della wiki usando Google Translate.
La traduzione potrebbe contenere errori e termini strani. Muovi il puntatore sopra al testo per vedere la versione originale. Puoi aiutarci a correggere gli gli errori. Per ulteriori istruzioni clicca qui. |
(Also see the list of type-related utilities that are provided by C++.)
Indice |
[modifica] Boolean type
- bool - type, capable of holding one of the two values: true or false.
[modifica] 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 (dal C++11)
- char32_t - type for UTF-32 character representation (dal C++11)
[modifica] 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).
[modifica] Modificatori
Modifies the integer type. Can be mixed in any order. Only one of each group can be present in type definition.
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 (dal C++11)
[modifica] 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: the C++ Standard guarantees that 1 == sizeof(char) <= sizeof(short) <= sizeof(int) <= sizeof(long) <= sizeof(long long).
[modifica] Data models
32 bit systems:
- LP32:
- Win16 API
- ILP32;
- Win32 API
- Unix and Unix-like systems (Linux, Mac OS X)
64 bit systems:
- LLP64
- Win64 API
- LP64
- Unix and Unix-like systems (Linux, Mac OS X)
[modifica] 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.
[modifica] 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 | ||
| floating point |
32 | IEEE-754 | ± 3.4 · 10± 38 (~7 digits) |
|
| 64 | IEEE-754 | ± 1.7 · 10± 308 (~15 digits) |
| |
[modifica] Parole chiave
bool, true, false, char, wchar_t, char16_t, char32_t, int, short, long, signed, unsigned, float, double
[modifica] Vedi anche
- <div class="t-tr-text"> cv specificatori</div>,Original:cv specifiersThe text has been machine-translated via [http://translate.google.com Google Translate].
You can help to correct and verify the translation. Click [http://en.cppreference.com/w/Cppreference:MachineTranslations here] for instructions. - <div class="t-tr-text"> Durata di stoccaggio specificatori</div>Original:storage duration specifiersThe text has been machine-translated via [http://translate.google.com Google Translate].
You can help to correct and verify the translation. Click [http://en.cppreference.com/w/Cppreference:MachineTranslations here] for instructions.
