[整理]C结构实现位段（bit field）

#include <stdio.h>
#include <string.h>

typedef struct A{
	int a:5;
	int b:3;
	unsigned c:8;
	unsigned d:8;
} Type_A;

/* VS2010, Windows XP, Debug模式下运行 */
int main(void)
{   
	struct A a;
	char s[]="12345678";

	printf( "%d\n",sizeof(Type_A) );//4
	printf("%d\n",sizeof(a));//4

	memcpy(&a,s,3);
	printf("%d\n",a.a);//‘1‘的低位 -15
	printf("%d\n",a.b);//‘1‘的高位 1
	printf("%d\n",a.c-‘0‘);//‘3‘ 51
	printf("%d\n",a.d-‘0‘);//‘4‘ 52

	return 0;
}