MCQ on constructor in C++: Multiple Choice Questions on C++ constructor

MCQ on constructor in C++ with answers and explanations for placement tests and job interviews. This C++ MCQ on constructor is useful for the campus placement for all freshers including Engineering Students, MCA students, Computer and IT Engineers, etc.

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Guideline of MCQ on constructor in C++:

This MCQ on constructor in C++ is intended for checking your knowledge of C++ constructors. It takes 30 minutes to pass the C++ quiz on the constructor. If you don’t finish the C++ constructor quiz within the mentioned time, all the unanswered questions will count as wrong. Every unanswered question will count as wrong. MCQ on constructor in C++ has randomization features that give you a new question set at every attempt.

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MCQ on constructor in C++

MCQ on constructor in C++: Multiple Choice Questions and Answers on constructor in C++

1 / 21

Predict the output of following program.

#include<iostream>
using namespace std;
class Point {
    int x;
public:
    Point(int x) { this->x = x; }
    Point(const Point p) { x = p.x;}
    int getX() { return x; }
};
 
int main()
{
   Point p1(10);
   Point p2 = p1;
   cout << p2.getX();
   return 0;
}

Compiler Error: p must be passed by reference

Garbage value

None of the above

2 / 21

Implicit return type of a class constructor is:

not of class type itself

class type itself

a destructor of class type

a destructor not of class type

3 / 21

Which of the followings is/are automatically added to every class, if we do not write our own.

Copy Constructor

Assignment Operator

A constructor without any parameter

All of the above

4 / 21

#include <iostream>
using namespace std;
 
class Test
{
public:
      Test() { cout << "Hello from Test() "; }
} a;
 
int main()
{
    cout << "Main Started ";
    return 0;
}

Main Started

Main Started Hello from Test()

Hello from Test() Main Started

Compiler Error: Global objects are not allowed

5 / 21

#include<iostream>
using namespace std;
 
class X 
{
public:
    int x;
};
 
int main()
{
    X a = {10};
    X b = a;
    cout << a.x << " " << b.x;
    return 0;
}

Compiler Error

10 followed by Garbage Value

10 10

10 0

6 / 21

When a copy constructor may be called?

When an object of the class is returned by value.

When an object of the class is passed (to a function) by value as an argument.

When an object is constructed based on another object of the same class

When compiler generates a temporary object.

All of the above

7 / 21

#include <iostream>
using namespace std;
 
class Point
{
    int x, y;
public:
   Point(int i = 0, int j = 0) { x = i; y = j; }
   int getX() { return x; }
   int getY() { return y; }
};
 
int main()
{
    Point p1;
    Point p2 = p1;
    cout << "x = " << p2.getX() << " y = " << p2.getY();
    return 0;
}

Compiler Error

x = 0 y = 0

x = garbage value y = garbage value

8 / 21

We must use initializer list in a constructor when

There is a reference variable in class

There is a constant variable in class

There is an object of another class. And the other class doesn't have default constructor.

All of the above

9 / 21

Predict the output of following program?

#include <iostream>
using namespace std;
class Test
{
private:
    int x;
public:
    Test(int i)
    {
        x = i;
        cout << "Called" << endl;
    }
};
 
int main()
{
    Test t(20);
    t = 30; // conversion constructor is called here.
    return 0;
}

Compiler Error

Called Called

Called

10 / 21

What is the output of following program?

#include <iostream>
using namespace std;
 
class Point
{
    int x, y;
public:
   Point(const Point &p) { x = p.x; y = p.y; }
   int getX() { return x; }
   int getY() { return y; }
};
 
int main()
{
    Point p1;
    Point p2 = p1;
    cout << "x = " << p2.getX() << " y = " << p2.getY();
    return 0;
}

x = garbage value y = garbage value

x = 0 y = 0

Compiler Error

11 / 21

Output?

#include<iostream>
#include<string.h>
using namespace std;
 
class String
{
    char *str;
public:
     String(const char *s);
     void change(int index, char c) { str[index] = c; }
     char *get() { return str; }
};
 
String::String(const char *s)
{
    int l = strlen(s);
    str = new char[l+1];
    strcpy(str, s);
}
 
int main()
{
   String s1("geeksQuiz");
   String s2 = s1;
   s1.change(0, 'G');
   cout << s1.get() << " ";
   cout << s2.get();
}

GeeksQuiz geeksQuiz

GeeksQuiz GeeksQuiz

geeksQuiz geeksQuiz

geeksQuiz GeeksQuiz

12 / 21

#include<iostream>
using namespace std;
  
class Test
{
public:
  Test();
};
  
Test::Test()  {
    cout << " Constructor Called. ";
}
  
void fun() {
  static Test t1;
}
  
int main() {
    cout << " Before fun() called. ";
    fun();
    fun();
    cout << " After fun() called. ";  
    return 0;
}

Constructor Called. Before fun() called. After fun() called.

Before fun() called. Constructor Called. Constructor Called. After fun() called.

Before fun() called. Constructor Called. After fun() called.

Constructor Called. Constructor Called. After fun() called.Before fun() called.

13 / 21

What is the right way to declare a copy constructor of a class if the name of the class is MyClass?

MyClass (constant MyClass *arg)

MyClass (constant MyClass &arg)

MyClass (MyClass arg)

MyClass (MyClass *arg)

14 / 21

Output of following program?

#include<iostream>
using namespace std;
 
class Point {
public:
    Point() { cout << "Normal Constructor calledn"; }
    Point(const Point &t) { cout << "Copy constructor calledn"; }
};
 
int main()
{
   Point *t1, *t2;
   t1 = new Point();
   t2 = new Point(*t1);
   Point t3 = *t1;
   Point t4;
   t4 = t3;
   return 0;
}

1.

Normal Constructor called
Normal Constructor called

Normal Constructor called

Copy Constructor called

Copy Constructor called

Normal Constructor called

Copy Constructor called

2.

Normal Constructor called
Copy Constructor called

Copy Constructor called

Normal Constructor called

Copy Constructor called

3.

Normal Constructor called
Copy Constructor called

Copy Constructor called

Normal Constructor called

15 / 21

Constructors have _____ return type.

void

char

int

16 / 21

Predict the output of following program.

#include<iostream>
#include<stdlib.h>
using namespace std;
 
class Test
{
public:
   Test()
   { cout << "Constructor called"; }
};
 
int main()
{
    Test *t = (Test *) malloc(sizeof(Test));
    return 0;
}

Constructor called

Empty

Compiler Error

Runtime error

17 / 21

#include<iostream>
using namespace std;
 
class Test
{
public:
   Test(Test &t) { }
   Test()        { }
};
 
Test fun()
{
    cout << "fun() Calledn";
    Test t;
    return t;
}
 
int main()
{
    Test t1;
    Test t2 = fun();
    return 0;
}

fun() Called

Empty Output

Compiler Error: Because copy constructor argument is non-const

18 / 21

Given the programming constructs i)assignment ii)for loops where the loop parameter cannot be changed within the loop iii)if-then-else iv)forward go to v)arbitrary go to vi)non-recursive procedure call vii)recursive procedure/function call viii)repeat loop, which constructs will you not include in a programming language such that it should be possible to program the terminates (i.e. halting) function in the same programming language.

ii), iii), iv)

v), vii), viii)

vi), vii), viii)

iii), v), viii)

19 / 21

Output of following program?

#include<iostream>
using namespace std;
class Point {
    Point() { cout << "Constructor called"; }
};
 
int main()
{
   Point t1;
   return 0;
}

Compiler Error

Runtime Error

Constructor called

20 / 21

Which of the following is true about constructors. 1) They cannot be virtual. 2) They cannot be private. 3) They are automatically called by new operator.

All 1, 2, and 3

Only 1 and 3

Only 1 and 2

Only 2 and 3

21 / 21

#include<iostream>
using namespace std;
class Point {
public:
    Point() { cout << "Constructor called"; }
};
 
int main()
{
   Point t1, *t2;
   return 0;
}

Compiler Error

Constructor called Constructor called

Constructor called

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MCQ on constructor in C++: Multiple Choice Questions on C++ constructor

Guideline of MCQ on constructor in C++:

You have 30 minutes to take the MCQs on Constructor in C++

Your time has been Over.

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