学点 C 语言(27): 数据类型 - 结构中的 "位字段"(2)
2. 用 8 个 Bit 构成一个 unsigned char 数:
#include
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();
return 0;
}
3. 包含位字段的结构和其他结构没有区别, 譬如同时包含其他类型的字段:
#include
int main(void)
{
struct Bit {
unsigned b1: 1;
unsigned b2: 1;
float f;
} B;
B.b1 = 0;
B.b2 = 1;
B.f = 3.14;
printf("%d, %d, %gn", B.b1, B.b2, B.f);
getchar();
return 0;
}
