Bit Field in C Language

#include<stdio.h>

struct bits
{
unsigned int a7:1;
unsigned int a6:1;
unsigned int a5:1;
unsigned int a4:1;
unsigned int a3:1;
unsigned int a2:1;
unsigned int a1:1;
unsigned int a0:1;
};

struct hexa
{
unsigned int h1:4;
unsigned int h0:4;
};

union u
{
char ch;
struct bits b;
struct hexa h;
}u1;

int main()
{
int i=70;
u1.ch=100;
printf("Bit Pattern for %c = ",u1.ch);
printf("%d %d %d %d %d %d %d %d",u1.b.a0,u1.b.a1,u1.b.a2,u1.b.a3,u1.b.a4,u1.b.a5,u1.b.a6,u1.b.a7);
//How to change Bit value
//u1.b.a6=1;
//u1.b.a7=0;
printf("\nHexa Decimal Value for %c = ",u1.ch);
printf("%x%x",u1.h.h0,u1.h.h1);

printf("\n\nSimple Conversion using printf :");
printf("\nDEC   =  %d",i);
printf("\nHexa  =  %X",i);
printf("\nOctal =  %o",i);

return 0;
}