Friend Function

#include<iostream.h>
#include<conio.h>
 class first;
 class second
 {
 int a;
 public:
 second()
 {
 a=3;
 }
 friend void sum(first , second );
 };

 class first
 {
 int b;
 public:
 first()
 {
 b=10;
 }
 friend void sum(first ,second );
 };

 void sum(first fobj, second sobj)
 {
 int s;
 s= fobj.b + sobj.a;
 cout<<"\n Sum is "<<s;
 }

void main()
 {
 clrscr();
 first f;
 second s;
 sum(f,s);
 getch();
 }