sizeof a union : sizeof « Operators statements « C++ Tutorial

1. C++ Tutorial
2. Operators statements
3. sizeof

#include<iostream.h>

union u_tag{
   int i;
   double d;
}u={88};
struct s_tag{
    int i;
       double d;
}s={66,1.234};

int main()
{
    int size;
       size=sizeof(union u_tag);
    cout<<"sizeof(union u_tag)="<<size<<endl;
    u.i=100;
       cout<<"u.i="<<u.i<<endl;
       u.d=1.2345;
       cout<<"u.d="<<u.d<<endl;
       size=sizeof(u.d);
       cout<<"sizeof(u.d)="<<size<<endl;
       cout<<"s.i="<<s.i<<endl;
       cout<<"s.d="<<s.d<<endl;
       size=sizeof(struct s_tag);
       cout<<"sizeof(struct s_tag)="<<size<<endl;
}

sizeof(union u_tag)=8
u.i=100
u.d=1.2345
sizeof(u.d)=8
s.i=66
s.d=1.234
sizeof(struct s_tag)=16