C++ friend keyword

Question 1

Predict the output of following program.

CPP

#include <iostream>
using namespace std;
class A
{
protected:
    int x;
public:
    A() {x = 0;}
    friend void show();
};

class B: public A
{
public:
    B() : y (0) {}
private:
    int y;
};

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

• Compiler Error in show() because x is protected in class A
• Compiler Error in show() because y is private in class b
• The default value of A::x = 0 The default value of B::y = 0
• Compiler Dependent

Question 2

Predict the output the of following program. 

C

#include <iostream>
using namespace std;

class B;
class A {
    int a;
public:
    A():a(0) { }
    void show(A& x, B& y);
};

class B {
private:
    int b;
public:
    B():b(0) { }
    friend void A::show(A& x, B& y);
};

void A::show(A& x, B& y) {
    x.a = 10;
    cout << \"A::a=\" << x.a << \" B::b=\" << y.b;
}

int main() {
    A a;
    B b;
    a.show(a,b);
    return 0;
}

• Compiler Error
• A::a=10 B::b=0
• A::a=0 B::b=0

Question 3

If a function is friend of a class, which one of the following is wrong?

• A function can only be declared a friend by a class itself.
• Friend functions are not members of a class, they are associated with it.
• Friend functions are members of a class.
• It can have access to all members of the class, even private ones.

Question 4

Which one of the following is correct, when a class grants friend status to another class?

• The member functions of the class generating friendship can access the members of the friend class.
• All member functions of the class granted friendship have unrestricted access to the members of the class granting the friendship.
• Class friendship is reciprocal to each other.
• There is no such concept.