C++ Programming

FRIENDS MCQs

Total Questions : 10

Question 1.

Where does keyword ‘friend’ should be placed?


  1.    function declaration
  2.    function definition
  3.    main function
  4.    None of the mentioned
 Discuss Question
Answer is Option A. -> function declaration

The keyword friend is placed only in the function declaration of the friend function and not in 

the function definition because it is used toaccess the member of a class.

Question 2.

Pick out the correct statement.


  1.    A friend function may be a member of another class.
  2.    A friend function may not be a member of another class.
  3.    A friend function may or may not be a member of another class.
  4.    None of the mentioned
 Discuss Question
Answer is Option C. -> A friend function may or may not be a member of another class.

None.

Question 3.


What is the output of this program?



1.
#include
2.
using namespace std;
3.
class sample
4.
{
5.
private:
6.
int a, b;
7.
public:
8.
void test()
9.
{
10.
a = 100;
11.
b = 200;
12.
}
13.
friend int compute(sample e1);
14.
};
15.
int compute(sample e1)
16.
{
17.
return int(e1.a + e1.b) - 5;
18.
}
19.
int main()
20.
{
21.
sample e;
22.
e.test();
23.
cout
  1.    100
  2.    200
  3.    300
  4.    295
 Discuss Question
Answer is Option D. -> 295

In this program, we are finding a value from the given function by using the friend for compute function.
Output:
$ g++ friend4.cpp
$ a.out
295

Question 4.


What is the output of this program?


1.
#include
2.
using namespace std;
3.
class base
4.
{
5.
int val1, val2;
6.
public:
7.
int get()
8.
{
9.
val1 = 100;
10.
val2 = 300;
11.
}
12.
friend float mean(base ob);
13.
};
14.
float mean(base ob)
15.
{
16.
return float(ob.val1 + ob.val2) / 2;
17.
}
18.
int main()
19.
{
20.
base obj;
21.
obj.get();
22.
cout << mean(obj);
23.
return 0;
24.
}

  1.    200
  2.    150
  3.    100
  4.    300
 Discuss Question
Answer is Option A. -> 200

In this program, We are finding the mean value by declaring the function mean as a friend of class base.
Output:
$ g++ friend3.cpp
$ a.out
200

Question 5.


What is the output of this program?



1.
#include
2.
using namespace std;
3.
class sample;
4.
class sample1
5.
{
6.
int width, height;
7.
public:
8.
int area ()
9.
{
10.
return (width * height);}
11.
void convert (sample a);
12.
};
13.
class sample
14.
{
15.
private:
16.
int side;
17.
public:
18.
void set_side (int a)
19.
{
20.
side = a;
21.
}
22.
friend class sample1;
23.
};
24.
void sample1::convert (sample a)
25.
{
26.
width = a.side;
27.
height = a.side;
28.
}
29.
int main ()
30.
{
31.
sample sqr;
32.
sample1 rect;
33.
sqr.set_side(6);
34.
rect.convert(sqr);
35.
cout
  1.    24
  2.    35
  3.    16
  4.    36
 Discuss Question
Answer is Option D. -> 36

In this program, we are using the friend for the class and calculating the area of the square.
Output:
$ g++ friend2.cpp
$ a.out
36

Question 6.


What is the output of this program?



1.
#include
2.
using namespace std;
3.
class sample
4.
{
5.
int width, height;
6.
public:
7.
void set_values (int, int);
8.
int area () {return (width * height);}
9.
friend sample duplicate (sample);
10.
};
11.
void sample::set_values (int a, int b)
12.
{
13.
width = a;
14.
height = b;
15.
}
16.
sample duplicate (sample rectparam)
17.
{
18.
sample rectres;
19.
rectres.width = rectparam.width * 2;
20.
rectres.height = rectparam.height * 2;
21.
return (rectres);
22.
}
23.
int main ()
24.
{
25.
sample rect, rectb;
26.
rect.set_values (2, 3);
27.
rectb = duplicate (rect);
28.
cout
  1.    20
  2.    16
  3.    24
  4.    None of the mentioned
 Discuss Question
Answer is Option C. -> 24

In this program, we are using the friend function for duplicate function and calculating the area 

of the rectangle.
Output:
$ g++ friend1.cpp
$ a.out
24

Question 7.

Which keyword is used to declare the friend function?


  1.    firend
  2.    friend
  3.    classfriend
  4.    myfriend
 Discuss Question
Answer is Option B. -> friend

None.

Question 8.

What is the syntax of friend function?


  1.    friend class1 Class2;
  2.    friend class;
  3.    friend class
  4.    None of the mentioned
 Discuss Question
Answer is Option A. -> friend class1 Class2;

In option a, the class2 is the friend of class1 and it can access all the private and protected 

members of class1.

Question 9.

Which rule will not affect the friend function?


  1.    private and protected members of a class cannot be accessed from outside
  2.    private and protected member can be accessed anywhere
  3.    both a & b
  4.    None of the mentioned
 Discuss Question
Answer is Option A. -> private and protected members of a class cannot be accessed from outside

Friend is used to access private and protected members of a class from outside the same class.

Question 10.


What is the output of this program?



1.
#include
2.
using namespace std;
3.
class Box
4.
{
5.
double width;
6.
public:
7.
friend void printWidth( Box box );
8.
void setWidth( double wid );
9.
};
10.
void Box::setWidth( double wid )
11.
{
12.
width = wid;
13.
}
14.
void printWidth( Box box )
15.
{
16.
box.width = box.width * 2;
17.
cout
  1.    40
  2.    5
  3.    10
  4.    20
 Discuss Question
Answer is Option D. -> 20

We are using the friend function for printwidth and multiplied the width value by 2, So we got the output as 20
Output:
$ g++ friend.cpp
$ a.out
20