C语言共用体（union）

程序：

#include "stdio.h"


typedef union
{
	struct
	{
		unsigned char D1;
		unsigned char D2;
		unsigned char D3;
		unsigned char D4;
		unsigned char D5;
	}u1_1;
	struct
	{
		unsigned char D1;
		unsigned char D2;
		unsigned char D3;
		unsigned char D4;
		unsigned char D5;
	}u1_2;
	unsigned char Data[5];
}union_u1; 



int main()
{
	union_u1 U1;
	U1.u1_1.D1=0X01;
	U1.u1_1.D2=0X02;
	U1.u1_1.D3=0X03;
	U1.u1_1.D4=0X04;
	U1.u1_1.D5=0X05;
	for(unsigned char i=0;i<5;i++)
		printf("Data[%d] = %#X \r\n",i,U1.Data[i]);
	printf("=============================\r\n");	
	U1.u1_2.D1=0X10;	
	U1.u1_2.D2=0X20;	
	U1.u1_2.D3=0X30;	
	U1.u1_2.D4=0X40;	
	U1.u1_2.D5=0X50;	
	for(unsigned char i=0;i<5;i++)
		printf("Data[%d] = %#X \r\n",i,U1.Data[i]);	
} 

运行结果：

分析：

同一个地址有三个别名

就好比如老鼠一样，英语叫mouse，在猫和老鼠又有叫杰瑞，其实都是指老鼠