Relive C + + (i)

Meaning of 0 and 1:

In the computer 0 and the switch representing the logic circuit, where 1 is closed and 0 is disconnected.

0 and 1 can be used to represent all the data in the computer, such as colors, pictures, videos, executable programs, such as can be made up of 32 0 000000000000000000~ representing white;

Binary:

2 The one in the binary is a bit, and 8 bits make up one byte;

Binary vs. decimal conversions:

Decimal, binary: a2a1a0=a0*2^0+a1*2^1+a2*2^2;

Decimal---binary: short division, dividing 10 binary number by 2 and the resulting quotient divided by 2, For example: 10->2 10/2=5 (remainder) 0,5/2=1 (remainder) 1,1/2=0 (remainder) 1, the corresponding binary is: 110

Variable:

When the program runs, it allocates memory space to the variable, and accessing the variable name actually accesses the memory space.

Types and ranges of variables:

Ref: 8790241

Machine Word length: Refers to the number of bits of binary data that a computer can handle in an integer operation (integer operation is a fixed-point integer operation). The machine word length is the length of the fixed-point arithmetic, usually the width of the internal data path of the CPU. It is now generally 32 bits, which is 4 bytes, and also 64-bit and 16-bit.

The arithmetic type of storage space is determined by the machine. In general, the short type is half machine word length, int is a machine word length, long is 1 or 2 machine word length, float is a machine length, double is two characters, long double is 3 or 4 words. The C + + standard specifies the minimum storage space for each arithmetic type, but it does not prevent the compiler from having larger storage space. If you want to ensure portability, try to use __int16 __int32 __int64 bar, or your own typedef int INT32 a bit.

Data type name	Number of bytes	Alias	Range of values
Int	*	signed,signed int	Determined by the operating system, which is related to the "word length" of the operating system
unsigned int	*	Unsigned	Determined by the operating system, which is related to the "word length" of the operating system
__int8	1	char,signed Char	–128 to 127
__int16	2	Short,short int,signed Short int	–32,768 to 32,767
__int32	4	signed,signed int	–2,147,483,648 to 2,147,483,647
__int64	8	No	–9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
bool	1	No	False or True
Char	1	Signed Char	–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
Long Long	8	None (but equivalent to __int64)	–9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
unsigned long	4	unsigned long int	0 to 4,294,967,295
Enum	*	No	Determined by the operating system, which is related to the "word length" of the operating system
Float	4	No	3.4E +/-(7 digits)
Double	8	No	1.7E +/-308 (digits)
Long double	8	No	1.7E +/-308 (digits)
wchar_t	2	__wchar_t	0 to 65,535

(P: The size of the pointer is a fixed value of 4 bytes)

The results in the 32-bit machine environment are as follows:

Type	Size	Range of values
No-value void	0 byte	No domain
boolean bool	1 byte	True False
signed short [int]/signed shorter [int]	2 byte	-32768~32767
Unsigned short-integer unsigned shorter [int]	2 byte	0~65535
Signed integral type int/signed [int]	4 byte	-2147483648~2147483647
unsigned integral type unsigned [int]	4 byte	0~4294967295
Signed long [int]/signed long [int]	4 byte	-2147483648~2147483647
unsigned long integer unsigned [int]	4 byte	0~4294967295
Long Long	8 byte	0~18446744073709552000
Signed character type char/signed Char	1 byte	-128~127
unsigned character type unsigned char	1 byte	0~255
Wide character type wchar_t (unsigned short.)	2 byte	0~65535
Single-precision float float	4 byte	-3.4e-38~3.4e+38
Double-precision floating-point double	8 byte	1.7e-308~1.7e+308
Long double	8 byte

The length of the specific type can be viewed with sizeof.

Signed integer calculation: treat the highest bit as a sign bit

The sign bit is 0: non-negative, and the remainder is even if the absolute value of the integer

The sign bit is 1: Negative number, the remaining digits equals the first absolute value of the integer plus 1; Take the absolute value-----plus 1

-1, 1000 0001, 1111 1110, 1111 1111
-2, 1000 0010, 1111 1101, 1111 1110

-3, 1000 0011, 1111 1100, 1111 1101

-4, 1000 0100, 1111 1011, 1111 1100

-5, 1000 0101, 1111 1010, 1111 1011

Constant definition: #define

Input and output:

\ "" means double quotation marks,

Relive C + + (i)