Go4Expert - notes and a sample program on freind function.

Hi all.:)

Here i m going to give imp. notes on friend functions..

description:-:crazy:
we knon that private members cannot be accessed from outside the class.This means that a non member function cannot have access to the private data of a class.
If we want to share the data ; in such situation C++ provide the use of friend function by which this problem can be solved.

Below there is a sample program to show the use of friend function....

code:

Code:

#include<iostream.h>

#include<conio.h>

class demo1;

class demo

{

 private:

 int x;

 int sum;

 float avg;

 public:

 void getdata()

 {

  cout<<"enter the valur for x"<<endl;

  cin>>x;

 }

 friend demo cal(demo d,demo1 d1);

 friend void show(demo d);

};

class demo1

{

 int y;

 public:

 void getdata()

 {

  cout<<"enter the value for y"<<endl;

  cin>>y;

 }

 friend demo cal(demo d,demo1 d1);

 //friend void show(demo d);

};

demo cal(demo d,demo1 d1)

{

 d.sum=0;

 d.avg=0;

 d.sum=d.sum+d.x+d1.y;

 d.avg=d.avg+d.sum/2;

 return d;

}

void show(demo d)

{

 cout<<"sum is"<<d.sum<<endl;

 cout<<"average is"<<d.avg;

}

void main()

{

 clrscr();

 demo d;

 demo1 d1;

 d.getdata();

 d1.getdata();

 d=cal(d,d1);

 show(d);

 getch();

}

note:- use of friend function is rarely done becoz it violates the rules of data hiding and encapsulation..

please reply to share more knowledge..... have a good day.:)