大端模式：高地址存放低字节；小端模式：高地址存放高字节；
例如 int num =0x12345678
| 内存地址 | 小端模式存放内容 | 大端模式存放内容 |
| 0x4000 | 0x78 | 0x12 |
| 0x4001 | 0x56 | 0x34 |
| 0x4002 | 0x34 | 0x56 |
| 0x4003 | 0x12 | 0x78 |
#include <stdio.h>
union num{
int int_num;
char char_num_union[2];
}num;
int main(int argc,char *argv[])
{
void *number=0;
num.char_num_union[0]=11;
num.char_num_union[1]=1;
printf("num.int_num:%d\n",num.int_num);
if(num.int_num == 267){
printf("小端\n");
}else if(num.int_num == 2817){
printf("大端\n");
}
num.int_num=0x1234;
printf("num.char_num_union[0] is %d,num.char_num_union[1] is %d\n",num.char_num_union[0],num.char_num_union[1]);
if(int(num.char_num_union[0]) == 18 && int(num.char_num_union[1]) == 52){
printf("大端\n");
}else if(int(num.char_num_union[0]) == 52 && int(num.char_num_union[1]) == 18){
printf("小端\n");
}
}
结果：
