Explain the output

Question

Please explain clearly how to find the output of the code below?

class A{
public:
void f() {cout <<1;}
};

class B : public A{
private:
void f() {cout <<2;}
};

void c(A &a) {a. f();}

int main(){
B b;
C(b);
}

Answer 1

class A is your base class.
class B is a derived class from A.

int main(){

// Instantiate an object of type B derived from type A
B b;

// This function call, feed object b by reference to friend function's "void C(A &a)" parameter list
C(b);
}

// This friend function with a ctor(copy constructor) as its parameter, assign an object of type B to A
void C(A &a) {

// invoking type A's f function using newly constructed object a
a.f();
}

As a result, "cout << 1" will be executed and you will have 1 on your console window.