Based on the review basic types -2

C values into basic types (integer: short, int, long; real: float, double, long double) and the character type char.

Integer

Integer is divided into short integer short, int int and long integer long. The number of bytes occupied by each type of bits associated with CPU

Types of	16-bit CPU	# 32	# 64
int	2 (btye)	4	4
unsigned int	2 (btye)	4	4
short	2	2	2
unsigned short	2 (btye)	2	2
long	4	4	8
unsigned long	4	4	8

Now generally used in 64-bit CPU.

unsigned unsigned, unsigned number is positive, a value ranging from zero.
For example:
int 64-bit CPU in the range of values represented [-2^31 , 2^31 - 1]
unsigned int 64-bit CPU in the range of value indicating [0, 2^32 - 1]
values are represented by the number 2 ^ 32

The number of different binary representations in C

In binary number 0b, or 0B(case insensitive) at the beginning, such as

int a = 0b101;  //换算成十进制为 5
int b = -0b110010;  //换算成十进制为 -50
int c = 0B100001;  //换算成十进制为 33
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Octal number to 0begin with, such as

int a = 015;  //换算成十进制为 13
int b = -0101;  //换算成十进制为 -65
int c = 0177777;  //换算成十进制为 65535
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Hex digits 0xor 0X(case insensitive) at the beginning, such as

int a = 0X2A;  //换算成十进制为 42
int b = -0XA0;  //换算成十进制为 -160
int c = 0xffff;  //换算成十进制为 65535
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On output, the value can not be binary output, only in decimal, octal, hexadecimal output. Output symbol

	short	int	long
Octal	% Ho	%O	%the
Decimal	%hd	%d	%ld
Hex	%hx 、%hX	%x、%X	%lx、%lX

Real

Real divided, float float, double, double, long double long double. Computer storage finite decimal precision, can not save many, many decimal places

Types of	Occupancy bytes	effective number
float	4 (btye)	6-7 place
double	8	15-16
long double	16

Output symbol %f, the default is after six decimal places, setting %.2fcan be to two decimal places.

float a = 3.14;
printf("%f -- %.2f\n", c，c);   //打印结果为  3.140000 -- 3.14
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Character Types

Char Character type, occupies only 1 byte, because the char variable is stored in memory corresponding to the ASCII value of the character, ASCII code value from 0 to 127, may be just a binary representation of the byte length. char type variable if the %coutput, according to the ASCII code table is converted to the corresponding characters; if the %doutput, or an integer.

char a = 'A';
int b = a;
printf("%c -- %d\n", a，b);   //打印结果为  A -- 65
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Byte long type conversion to short-byte type assignment, truncation will occur, such as int -> char when, will retain the low byte int, char length of the high byte exceeds the discard.
Conversely expansion occurs, the under-byte complement, complement 0 positive, negative, up 1

Operation

When different types of operation, type conversion occurs

Byte short line to long byte
Signed in line to the unsigned
Integer in line to float
Line to the double-precision single-precision

First conversion type, and then calculated.

Increment, decrement

i++And ++i, i--and --i. After symbol, compared with the value before the operation. Previous symbol, taken after calculation, i.e.,

int i = 0 ;
int j = i++ ;   // i = 1， j = 0
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int i = 0 ;
int j = ++i ;   // i = 1， j = 1
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int i = 0 ;
int j = i--;    // i = -1， j = 0
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int i = 0 ;
int j = --i;    // i = -1， j = -1
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Increment decrement operation can only variables, constants can not operate, such as ++0the like is wrong

Composite Operators

It refers to a compound operator *=, +=, -=and the like of the operator, the right combination.

int i = 0;
i += 2;             // i = i + 2;          
i *= 3;             // i = i * 3;
printf("%d\n",i);    //  6
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