UC知道但请问此处
来源：百度知道 编辑：UC知道 时间：2024/07/04 18:58:58
#include <stdio.h>
int main(void)
{
struct Bit {
int b8: 1;
int b7: 1;
int b6: 1;
int b5: 1;
int b4: 1;
int b3: 1;
int b2: 1;
int b1: 1;
} B;
unsigned char *p = NULL;
B.b1 = 1; B.b2 = 1; B.b3 = 1; B.b4 = 1; B.b5 =1; B.b6 = 1; B.b7 = 1; B.b8 = 1;
p = (unsigned char *)&B;
printf("%dn", *p); /* 255 */
B.b1 = 0; B.b2 = 0; B.b3 = 0; B.b4 = 0; B.b5 = 0; B.b6 = 0; B.b7 = 0; B.b8 = 1;
p = (unsigned char *)&B;
printf("%dn", *p); /* 1 */
B.b1 = 0; B.b2 = 0; B.b3 = 0; B.b4 = 0; B.b5 = 1; B.b6 = 1; B.b7 = 1; B.b8 = 1;
p = (unsigned char *)&B;
printf("%dn", *p); /* 15 */
B.b1 = 0; B.b2 = 1; B.b3 = 1; B.b4 = 1; B.b5 = 1; B.b6 = 1; B.b7 = 1; B.b8 = 1;
p = (unsigned char *)&B;
printf("%dn", *p); /* 127 */
getchar();
int main(void)
{
struct Bit {
int b8: 1;
int b7: 1;
int b6: 1;
int b5: 1;
int b4: 1;
int b3: 1;
int b2: 1;
int b1: 1;
} B;
unsigned char *p = NULL;
B.b1 = 1; B.b2 = 1; B.b3 = 1; B.b4 = 1; B.b5 =1; B.b6 = 1; B.b7 = 1; B.b8 = 1;
p = (unsigned char *)&B;
printf("%dn", *p); /* 255 */
B.b1 = 0; B.b2 = 0; B.b3 = 0; B.b4 = 0; B.b5 = 0; B.b6 = 0; B.b7 = 0; B.b8 = 1;
p = (unsigned char *)&B;
printf("%dn", *p); /* 1 */
B.b1 = 0; B.b2 = 0; B.b3 = 0; B.b4 = 0; B.b5 = 1; B.b6 = 1; B.b7 = 1; B.b8 = 1;
p = (unsigned char *)&B;
printf("%dn", *p); /* 15 */
B.b1 = 0; B.b2 = 1; B.b3 = 1; B.b4 = 1; B.b5 = 1; B.b6 = 1; B.b7 = 1; B.b8 = 1;
p = (unsigned char *)&B;
printf("%dn", *p); /* 127 */
getchar();
直接看内存就知道了
各个工具应该都能查看变量的memory dump
8位的2进制数，可以自己算算~
11111111
00000001
00001111
01111111
struct Bit是位结构。
位结构是一种特殊的结构, 在需按位访问一个字节或字的多个位时, 位结构比按位运算符更加方便。位结构定义的一般形式为:
struct位结构名{
数据类型 变量名: 整型常数;
数据类型 变量名: 整型常数;
} 位结构变量;
其中: 数据类型必须是int(unsigned或signed)。整型常数必须是非负的整数, 范围是0~15, 表示二进制位的个数, 即表示有多少位。
Bit实际上就是定义了一个字节的8位，具体数值自己算算就清楚了。
字符型的变量的范围是128-255；