C++ Friend Function Aptitude Questions and Answers

1) There are the following statements that are given below, which of them are correct about the friend in C++?

1. A friend is a keyword in C++.
2. A friend keyword is used to violate the rules of data encapsulation in C++.
3. A friend keyword is used to access the private members of the class.
4. A friend keyword is used to access the protected members of the class.

Options:

1. A and B
2. A and C
3. A, B, and C
4. A, B, C, and D

2) In C++, the friend can be used with?

1. Member functions
2. Non-member functions
3. Class
4. All of the above

Options:

1. A and B
2. A and C
3. B and C
4. D

3) What is the correct output of the given code snippets?

#include <iostream>
using namespace std;

int main()
{
    friend int A = 10;
    cout << A << endl;
    return 0;
}

Options:

1. 10
2. Compilation error
3. Runtime error
4. Linker error

4) What is the correct output of the given code snippets?

#include <iostream>
using namespace std;

friend void fun()
{
    cout << "hello world" << endl;
}

int main()
{
    fun();
    return 0;
}

Options:

1. hello world
2. Compilation error
3. Runtime error
4. Linker error

5) What is the correct output of the given code snippets?

#include <iostream>
using namespace std;

void fun();

class Sample {
private:
    int var;

public:
    Sample()
    {
        var = 10;
    }
    friend void fun();
};

void fun()
{
    Sample S;

    cout << S.var << endl;
}

int main()
{
    fun();
    return 0;
}

Options:

1. 10
2. Compilation error
3. Runtime error
4. Linker error

6) What is the correct output of given code snippets in C++?

#include <iostream>
using namespace std;

class Sample {
private:
    int var;

public:
    Sample()
    {
        var = 10;
    }
    friend void fun();
};

void fun()
{
    Sample S;

    cout << S.var << endl;
}

int main()
{
    fun();
    return 0;
}

Options:

1. 10
2. Compilation error
3. Runtime error
4. Linker error

7) What is the correct output of given code snippets in C++?

#include <iostream>
using namespace std;

class Sample {
private:
    int var;

public:
    Sample()
    {
        var = 10;
    }
    friend void fun();
};

friend void fun()
{
    Sample S;

    cout << S.var << endl;
}

int main()
{
    fun();
    return 0;
}

Options:

1. 10
2. Compilation error
3. Runtime error
4. Linker error

8) Can we access private data members of class outside without using a friend function?

1. Yes
2. No

9) What is the correct output of the given code snippets?

#include <iostream>
using namespace std;

class SampleA {
private:
    int var;

public:
    SampleA()
    {
        var = 10;
    }
    friend void fun();
};

class SampleB {
private:
    int var;

public:
    SampleB()
    {
        var = 20;
    }
    friend void fun();
};

void fun()
{
    SampleA Ob1;
    SampleB Ob2;

    cout << Ob1.var << ", " << Ob2.var << endl;
}

int main()
{
    fun();
    return 0;
}

Options:

1. 10, 20
2. 10
3. Garbage Value
4. Compilation error

10) What is the correct output of the given code snippets?

#include <iostream>
using namespace std;

class SampleA {
private:
    int var;

public:
    SampleA()
    {
        var = 10;
    }
    friend void fun();
};

class SampleB {
private:
    int var;

public:
    SampleB()
    {
        var = 20;
    }
    friend void fun();
};

void fun(SampleA A, SampleB B)
{
    cout << A.var << "," << B.var << endl;
}

int main()
{
    SampleA Ob1;
    SampleB Ob2;

    fun(ob1, ob2);
    return 0;
}

Options:

1. 10, 20
2. 10
3. Garbage Value
4. Compilation error

11) What is the correct output of given code snippets?

#include <iostream>
using namespace std;

class SampleA {
private:
    int var;

public:
    SampleA()
    {
        var = 10;
    }
    friend class SampleB;
};

class SampleB {
private:
    int var;

public:
    SampleB()
    {
        SampleA A;
        var = 20;

        cout << var << ", " << A.var;
    }
};

int main()
{
    SampleB B;
    return 0;
}

Options:

1. 10, 20
2. 20, 10
3. Garbage Value
4. Compilation error

12) What is the correct output of the given code snippets?

#include <iostream>
using namespace std;

class SampleA {
private:
    int var;

public:
    SampleA()
    {
        SampleB B;

        var = 10;

        cout << var << ", " << B.var;
    }
    friend class SampleB;
};

class SampleB {
private:
    int var;

public:
    SampleB()
    {
        var = 20;
    }
};

int main()
{
    SampleB B;
    return 0;
}

Options:

1. 10, 20
2. 20, 10
3. Garbage Value
4. Compilation error

13) What is the correct output of given code snippets?

#include <iostream>
using namespace std;

class SampleA {
private:
    int var;

public:
    SampleA()
    {
        var = 10;
    }
    friend void SampleB::fun();
};

class SampleB {
private:
    int var;

public:
    SampleB()
    {
        SampleA A;

        var = 20;
        cout << A.var << ", ";
    }
    void fun()
    {
        cout << var << endl;
    }
};

int main()
{
    SampleB B;

    B.fun();
    return 0;
}

Options:

1. 10
2. 20, 10
3. 20
4. Compilation error

14) What is the correct output of given code snippets?

#include <iostream>
using namespace std;

class B;

class ABC {
public:
    void fun();
};

class XYZ {
private:
    int var;

public:
    XYZ()
    {
        var = 10;
    }
    friend void ABC::fun();
};

void ABC::fun()
{
    XYZ ob;
    cout << ob.var;
}

int main()
{
    ABC a;
    a.fun();
    return 0;
}

Options:

1. 10
2. 20
3. Compilation error
4. Runtime error

15) Suppose if class A is a friend of class B, then class B will also be a friend of class A?

1. Yes
2. No