Friend Class in C++

By Akansh Upadhyay

In this guide we will see the concept of friend class, it's usage and program in C++.

What is Friend Class?

A friend class is a class that accesses the private and protected members of another class which is declared as friend. It is beneficial if a user wants to access a private class of another class. We use the keyword friend to declare friend class.

Syntax:

class X{
  private:
    //.....
  protected:
    //.....
  function()
  {
    //Statements
  }
  friend class Y;
};
class Y{
  private:
    ....
  public:
    function(X ob)
    {
      //Statements
    }
};

Advantage of Friend Class:

1. We can access private and protected members of other classes.

2. Enables classes to share private members' information.

3. Beneficial if classes have the same type of data members.

Program:

#include
using namespace std;
class St1{
  public:
    int rollno,marks;
    void gdetail()
    {
      cout<<"Enter roll no. ";
      cin>>rollno;
      cout<<"Enter Marks ";
      cin>>marks;
    }
  friend class St2;
};
class St2{
  public:
    int r,m,avg;
    void data()
    {
      cout<<"\nEnter roll no. ";
      cin>>r;
      cout<<"Enter marks ";
      cin>>m;
    }
    void average(St1 ob)
    {
      avg=(ob.marks+m)/2;
      cout<<"\nThe average marks= "<<avg;
    }
  
};
int main()
{
  St1 x;
  St2 y;
  x.gdetail();
  y.data();
  y.average(x);
}

Output: