结构体位制 中存在 有符号 与 无符号 -- C

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
/*
	有符号 结构体1
*/
struct bits
{
	int b1:5;
	/*
		由于是int型，最大设置32位。由于int型是有符号整形,
		所以这里5位为有符号类型。
		11111 -1
		10000 -16
		01111 15
		00000 0
	*/
 
	int :2;
 
	int b2:2;
	/*
		11 -1
		10 -2
		01 1
		00 0
	*/
 
	int b3:1;
	/*
		1 -1
		0 0
	*/
 
};
 
/*
	无符号 结构体2
*/
struct bits
{
	unsigned int b1:5;
	unsigned int :2;
	unsigned int b2:2;
	unsigned int b3:1;
};
 
int
main()
{
	struct bits b;
//	int a = 0b1111111111111111;
	int a = 0b0100110101000101;
 
	memcpy(&b, &a, sizeof(b));
//	memcpy(&b, "EM", sizeof(b));
	printf("0x%X\n", b);
	printf("b.b1 = %d\n", b.b1);
	printf("b.b2 = %d\n", b.b2);
	printf("b.b3 = %d\n", b.b3);
}
/*
int a = 0b0100110101000101;
0x4D45
b.b1 = 5
b.b2 = -2
b.b3 = 0
 
int a = 0b1111111111111111;
0xFFFF
b.b1 = -1
b.b2 = -1
b.b3 = -1
 
int a = 0b0100110101000101;
0x4D45
b.b1 = 5
b.b2 = 2
b.b3 = 0
 
int a = 0b1111111111111111;
0xFFFF
b.b1 = 31
b.b2 = 3
b.b3 = 1
 
*/