Inheritance and Friendship in C++

In this tutorial, we will look into what Inheritance and Friendship in C++ are, as well as the differences between the two.

What is Inheritance in C++:

In C++, inheritance is an OOPS concept. It permits the creation of classes that are derived from other classes and so incorporate some of the base class's functionality as well as some of its own capabilities.

What is Friendship in C++:

Members of a class that are private or protected are normally inaccessible from outside the class in which they are described. A buddy class, on the other hand, has access to the first's protected and secret members. Friendship classes offer access to not only public members, but also private and protected members.

Difference between Inheritance and Friendship in C++:

Friendship is not inherited in C++. If a base class has a friend function, the method is not inherited by the derived class (es).

The following code, for example, produces an error because show (), a friend of base class P, tries to access private data of derived class Q.

C++ Program:

#include <iostream>
using namespace std;


class P {
protected:
	int a;


public:
	P() { a = 0; }
	friend void show();
};
class Q : public P {
private:
	int b;


public:
	Q() { b = 0; }
};


void show()
{
	Q q;
	cout << "The default value of A::x = " << q.a;
	cout << "The default value of B::y = " << q.b;
}


int main()
{
	show();
	getchar();
	return 0;
}

Output:

C:\Users\Anonymous\Documents\Untitled1.cpp	In function 'void show()':
15	6	C:\Users\Anonymous\Documents\Untitled1.cpp	[Error] 'int Q::b' is private
25	46	C:\Users\ Anonymous\Documents\Untitled1.cpp	[Error] within this context