unsigned 变量名:n

/*
 * size是字节数
 * addr是打印的起始地址
 */
static void printb(void * addr,size_t size){
    for(int i=0;i<size;i++){
        uint8_t tmpChar=((uint8_t*)addr)[i];
//        printf("%x ",tmpChar);
        for(int j=0;j<8;j++){
            uint8_t get_value=1<<(8-j-1);
            printf("%d",(get_value&tmpChar)?1:0);
        }
        printf(" ");
    }
    printf("\n");

}

int main(int argc, char **argv) {
    struct test {
        unsigned a :2;
        unsigned b :1;
        unsigned c :1;
        unsigned d :1;
    };
    test t;
    memset(&t,0,sizeof(t));
    t.a=2;
    t.b=1;
    t.c=0;
    t.d=1;
    printf("%d\n", sizeof(t));
    printb(&t,sizeof(t));
}

4
00010110 00000000 00000000 00000000