C++ | friend keyword | Question 2

Predict the output the of following program.

#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; 
} 

(A) Compiler Error
(B) A::a=10 B::b=0
(C) A::a=0 B::b=0

Answer: (B)

Explanation: This is simple program where a function of class A is declared as friend of class B.

Since show() is friend, it can access private data members of B.

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