A program to explain UNIONS

#include <stdio.h>
#include <string.h>
 
union student
{
    char name[15];
    int rn;
};
 
void main()
{
    union student u;
    strcpy(u.name, "John");
    printf("Name = %s\n", u.name);
 
    u.rn = 123; // u.name now contains garbage value
    printf("Roll number = %d\n", u.rn);
 
    printf("\n");
}