What is a friend class?

The concept of encapsulation and data hiding indicate that nonmember functions should not be able to access an object’s private and protected data. The policy is if you are not a member, you can’t get it. But there is a certain situation wherein you need to share your private or protected data with nonmembers. ‘Friends’ come here as a rescue.

A friend class is a class whose member functions can access another class’ private and protected members. Ex.:

class ABC
{
private:
  int x;
  int y;
public:
  void getvalue(void)
  {
    cout << "Enter the values : ";
    cin >> x >> y;
  }
  friend float avg(ABC A);
};
float avg(ABC A)
{
  return float(A.x + A.y)/2.0;
}
int  main()
{
  ABC obj;
  Obj.getvalue();
  float av;
  av = avg(obj);
  cout << "Average = " << av;
  return 0;
}

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