程序代码：

#include <stdio.h>
#define N 12

int main(void)
{
    struct {
        unsigned char bin:2;
    } b;
    int i;

    printf ("repeat 4 num\n");
    b.bin = 0;
    for (i=1; i<=N; i++)
        printf ("%d\n", b.bin++);
    printf ("repeat 3 num\n");
    b.bin = 0;
    for (i=1; i<=N; i++) {
        printf ("%d\n", b.bin++);
        b.bin += b.bin & (b.bin>>1); // 只比上面多了这句
    }
    return 0;
}