The determination of C + + numerical range in VC

1. The Visual C + + 32-bit and 64-bit compilers recognize the types in the tables later in this article.

If the name starts with two underscores ( __ ), the data type is non-standard.

The ranges specified in the following table contain both a start value and an end value.

type name	bytes	Other Name	range of Values
Int	4	Signed	–2,147,483,648 to 2,147,483,647
unsigned int	4	Unsigned	0 to 4,294,967,295
__int8	1	Char	–128 to 127
unsigned __int8	1	unsigned char	0 to 255
__int16	2	short, short int, signed short int	–32,768 to 32,767
unsigned __int16	2	unsigned short, unsigned short int	0 to 65,535
__int32	4	Signed, signed int, int	–2,147,483,648 to 2,147,483,647
unsigned __int32	4	unsigned, unsigned int	0 to 4,294,967,295
__int64	8	Long long, signed long long	–9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
unsigned __int64	8	unsigned long long	0 to 18,446,744,073,709,551,615
bool	1	No	False or True
Char	1	No	128 to 127 (default) 0 to 255 (when compiling with/j)
Signed Char	1	No	–128 to 127
unsigned char	1	No	0 to 255
Short	2	short int, signed short int	–32,768 to 32,767
unsigned short	2	unsigned short int	0 to 65,535
Long	4	Long int, signed long int	–2,147,483,648 to 2,147,483,647
unsigned long	4	unsigned long int	0 to 4,294,967,295
Long Long	8	None (equivalent to __int64)	–9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
unsigned long long	8	None (equivalent to unsigned __int64)	0 to 18,446,744,073,709,551,615
Enum	Varies	No	See remarks later in this article
Floating	4	No	3.4E +/-38 (7-digit)
Double	8	No	1.7E +/-308 (15-digit)
Long double	Same as Double	No	Same as Double
wchar_t	2	__wchar_t	0 to 65,535

2. Code portability issues, because the language standard allows portable code to be implementation-specific, it is recommended that you do not use the _ _ IntX type Because this is a data type unique to Microsoft VC.

(1) int and unsigned``int type have a size of four bytes.

However, because the language standard allows portable code to be implementation-specific, the code should not depend on int the size.

(2) The __intn type specifier declares a 8-bit, 16-bit, 32-bit, or 64-bit integer variable, where n is 8, 16, 32, or 64.

Endl

The determination of C + + numerical range in VC