Using struct to represent bit fields

#include <stdio.h>

struct packed_data
{
    unsigned int :3;
    unsigned int f1:1;
    unsigned int f2:1;
    unsigned int f3:1;
    unsigned int type:8;
    unsigned int index:18;
};
int main(void)
{

    struct packed_data pd;
    pd.type = 257;
    printf("%u\n", pd.type);

    pd.f1 = 4;
    printf("%u\n", pd.f1);

    //printf("%p\n", &(pd.f1));         ERROR

    return 0;
}