01  #include<stdio.h>
02  
03  union My
04  {
05  int x;
06  float y;
07  char z;
08  }u;
09  
10  
11  int main()
12  {
13  u.x=10;
14  printf("x = %d  n",u.x);
15  
16  u.y=9.8;
17  printf("y = %f  n",u.y);
18  
19  u.z='a';
20  printf("z = %c  n",u.z);
21  
22  return 0;
23  }

OUTPUT 
x = 10
y = 9.800000
z = a