Size end byte order

One 、 What is size side byte order

• data-high ： for example 16 Hexadecimal number 0x123456789,0x12 That is, the high-order data , relative ,0x89 Is the low order of data

• High address space ： For example, the following address 0x00000002 Is the upper address space , relative , Address 0x00000001 Is the lower address space
  

• Small endian byte order (LSB)： Store the high bits of data in the high address space

• Big endian byte order (HSB)： Store the high bits of data in the low address space

• summary ： Small end sequence , Large end reverse order

  • The order It refers to the high-low bit order of data and the high-low order of address In the same direction
  • The reverse It refers to the high-low bit order of data and the high-low order of address In the opposite direction
    
    

Two 、 Code testing

• Different cpu（ The big and small end is made up of cpu Decisive ） There are different strategies for storing data ：
• Use the following code to determine what byte order the computer uses

#include <stdio.h>
int main()
{
    
    int a = 0x12345678;
    char *b = (char *)&a;// Use char The type pointer is a value that you want to take only 1Byte
    if(*b == 0x12)
        printf(" Big end \n");
    else if(*b == 0x78)
        printf(" The small end \n");
    return 0;
}

• Usually computers use small endian byte order to store data , The data transmission in the network adopts large end byte order