Friend Functions and Friend Classes Interview Questions

    Question 1: C++ OOPS Friend Function Concept

    What is the main purpose of a friend function in C++?

    Question 2: C++ OOPS Friend Function Syntax

    Which keyword is used to declare a friend function inside a class?

    Question 3: C++ OOPS Friend Function Example

    What will be the output of this code?

    #include <iostream>
using namespace std;
class Box {
    int length;
public:
    Box() { length = 10; }
    friend void printLength(Box);
};
void printLength(Box b) {
    cout << b.length;
}
int main() {
    Box b;
    printLength(b);
}

    Question 4: C++ OOPS Friend Function and Encapsulation

    Does declaring a function as a friend violate encapsulation?

    Question 5: C++ OOPS Friend Function Multiple Classes

    What will be the output?

    #include <iostream>
using namespace std;
class A {
    int x = 5;
    friend class B;
};
class B {
public:
    void show(A a) { cout << a.x; }
};
int main() {
    A a;
    B b;
    b.show(a);
}

    Question 6: C++ OOPS Friend Class Concept

    Which statement is true about friend classes in C++?

    Question 7: C++ OOPS Friend Function and Object Passing

    What will be the output?

    #include <iostream>
using namespace std;
class Number {
    int value;
public:
    Number(int v) { value = v; }
    friend int getValue(Number n);
};
int getValue(Number n) {
    return n.value;
}
int main() {
    Number n(42);
    cout << getValue(n);
}

    Question 8: C++ OOPS Friend Function vs Member Function

    Which of the following is true?

    Question 9: C++ OOPS Operator Overloading with Friend Function

    What will be the output?

    #include <iostream>
using namespace std;
class Complex {
    int real;
public:
    Complex(int r) : real(r) {}
    friend Complex operator+(Complex c1, Complex c2);
    void show() { cout << real; }
};
Complex operator+(Complex c1, Complex c2) {
    return Complex(c1.real + c2.real);
}
int main() {
    Complex a(3), b(4);
    Complex c = a + b;
    c.show();
}

    Question 10: C++ OOPS Limitations of Friend Functions

    Which of the following is NOT true about friend functions in C++?