3, 大小端问题

1,留个代码，便于遗忘后快速想起来。

#include <stdio.h>

int main()
{
    union
    {
        unsigned char sa[4];
        unsigned long lv;
    }u2;
    u2.lv = 0x12345678;
    printf("%x\n", u2.sa[0]); //输出78,低位低地址,  原来是小端.

    union
    {
        unsigned short sa[2];
        unsigned long lv;
    }u;
    u.sa[0] = 10;
    u.sa[1] = 20;
    printf("%x\n", u.lv); //输出:14000a  (小端,高位放在高地址)
    return 0;
}