C++ OOPs Concepts Quiz - MCQ Questions and Answers

Welcome to our "C++ OOPs Concepts Quiz - 25 MCQ Questions and Answers" blog post! Whether you're a budding programmer, a student preparing for exams, or a professional looking to brush up on your C++ Object-Oriented Programming skills, this quiz is crafted to challenge and reinforce your understanding of core OOP principles in C++. 

Dive into a series of carefully selected multiple-choice questions that cover everything from basic concepts to more advanced aspects of OOP in C++. Test your knowledge, learn through practice, and see where you stand in the world of object-oriented programming with C++. Let's get started!

1. What is Object-Oriented Programming (OOP) in C++?

a) A programming paradigm based on the concept of functions

b) A programming style based on the concept of classes and objects

c) A way to program with an emphasis on procedural logic

d) A method of programming focused solely on data

Answer:

b) A programming style based on the concept of classes and objects

Explanation:

Object-Oriented Programming in C++ is a programming paradigm that uses classes and objects to encapsulate data and operations on data, promoting concepts like inheritance, polymorphism, encapsulation, and abstraction.

2. What is a class in C++?

a) A function that defines operations on data

b) A template for creating objects

c) A collection of variables

d) A data type defined by the user

Answer:

b) A template for creating objects

Explanation:

A class in C++ is a blueprint or template for creating objects. It defines properties (data members) and behaviors (member functions or methods) of an object.

3. What is an object in C++?

a) A variable of a fundamental data type

b) An instance of a class

c) A function inside a class

d) A method of data manipulation

Answer:

b) An instance of a class

Explanation:

An object in C++ is an instance of a class. It is created from a class and represents a real-world entity with attributes (data members) and behaviors (member functions).

4. What is encapsulation in C++?

a) The process of inheriting properties from another class

b) The process of combining data and functions into a single unit called class

c) The ability of an object to take many forms

d) The capability to hide the internal implementation of an object

Answer:

b) The process of combining data and functions into a single unit called class

Explanation:

Encapsulation in C++ is the concept of bundling data (variables) and methods (functions) that work on the data into a single unit, or class, to hide the details and complexity from the user.

5. What is inheritance in C++?

a) Sharing data between classes

b) Deriving new classes from existing classes

c) Copying properties of one class into another

d) Changing the behavior of a function

Answer:

b) Deriving new classes from existing classes

Explanation:

Inheritance in C++ is a mechanism where a new class (derived class) inherits the properties and behavior of an existing class (base class). This allows for code reusability and hierarchical classification.

6. What is polymorphism in C++?

a) The ability to define multiple functions with the same name

b) The ability of a message to be displayed in more than one form

c) The ability of different classes to have methods with the same name

d) The ability of a class to have multiple constructors

Answer:

c) The ability of different classes to have methods with the same name

Explanation:

Polymorphism in C++ is the ability of entities such as functions or objects to process data in more than one form. It allows methods with the same name to behave differently in different contexts or classes.

7. What are virtual functions in C++?

a) Functions that exist only in virtual classes

b) Functions that cannot be implemented

c) Member functions that are overridden in derived classes

d) Functions that are declared with the keyword 'virtual'

Answer:

d) Functions that are declared with the keyword 'virtual'

Explanation:

Virtual functions in C++ are member functions declared in the base class using the 'virtual' keyword and are meant to be overridden in derived classes. They enable runtime polymorphism.

8. What is an abstract class in C++?

a) A class that cannot be instantiated

b) A class with no member functions

c) A class derived from another abstract class

d) Any class in C++

Answer:

a) A class that cannot be instantiated

Explanation:

An abstract class in C++ is a class that cannot be instantiated on its own. It typically contains at least one pure virtual function and is intended to be a base class for other classes.

9. What is a constructor in C++?

a) A special function used to initialize objects of its class

b) A function that destroys an object

c) A normal function declared inside a class

d) A static member function of a class

Answer:

a) A special function used to initialize objects of its class

Explanation:

A constructor in C++ is a special member function that is automatically called when an object of the class is created. It is used to initialize the object's properties.

10. What is operator overloading in C++?

a) Changing the way operators work in C++

b) Using an operator more than once in a program

c) Providing a new definition to an existing operator

d) Overloading a function based on its return type

Answer:

c) Providing a new definition to an existing operator

Explanation:

Operator overloading in C++ is a feature that allows operators to be redefined and used in different ways, depending on their operands. It enables operators to operate on user-defined types.

11. What is a destructor in C++?

a) A function that initializes an object

b) A special function that is called when an object goes out of scope

c) A member function that deletes an object

d) A static function that destroys all objects of a class

Answer:

b) A special function that is called when an object goes out of scope

Explanation:

A destructor in C++ is a special member function that is automatically called when an object goes out of scope or is explicitly deleted. It is used to release resources that the object may have acquired during its lifetime.

12. What is a copy constructor in C++?

a) A constructor that copies data from one object to another

b) A default constructor provided by the compiler

c) A constructor used to create a copy of a given object

d) A constructor that initializes an object from another object of the same class

Answer:

d) A constructor that initializes an object from another object of the same class

Explanation:

A copy constructor in C++ is a special constructor that initializes a new object from an existing object of the same class. It is used when an object is passed by value or returned from a function.

13. What is meant by function overloading in C++?

a) Defining multiple functions with the same name but different parameters

b) Changing the return type of a function

c) Overloading an operator function

d) Calling a function with too many arguments

Answer:

a) Defining multiple functions with the same name but different parameters

Explanation:

Function overloading in C++ is the ability to create multiple functions with the same name but different numbers or types of parameters. It allows functions to perform similar operations with different types or numbers of arguments.

14. What is the use of the 'this' pointer in C++?

a) To store the address of the currently executing function

b) To pass an object as an argument to another function

c) To refer to the current object instance

d) To create a new object

Answer:

c) To refer to the current object instance

Explanation:

The 'this' pointer in C++ is a special pointer used within a class, which points to the current object instance. It is used to access the members of the object on which a member function is called.

15. What is a pure virtual function in C++?

a) A function that can only be called from a derived class

b) A virtual function that has no definition

c) A function that is defined in a base class and overridden in a derived class

d) A virtual function that is declared but not implemented

Answer:

d) A virtual function that is declared but not implemented

Explanation:

A pure virtual function in C++ is a virtual function that is declared in a base class but has no implementation in that class, typically represented with '= 0' in its declaration. It must be overridden in derived classes.

16. What is meant by data hiding in C++?

a) Keeping data members private to a class

b) Deleting data from an object

c) Hiding the data of one class from another

d) Encrypting data within a class

Answer:

a) Keeping data members private to a class

Explanation:

Data hiding in C++ is the practice of keeping data members private or protected in a class. This prevents direct access to these members from outside the class, ensuring encapsulation.

17. What is the difference between a class and a struct in C++?

a) 'struct' is used for data-only structures, while 'class' can have both data and functions

b) In 'struct', members are public by default, while in 'class', they are private by default

c) 'struct' cannot have member functions, while 'class' can

d) 'class' is a newer concept in C++, while 'struct' is deprecated

Answer:

b) In 'struct', members are public by default, while in 'class', they are private by default

Explanation:

The primary difference between a class and a struct in C++ is the default access level of their members. In a class, members are private by default, whereas, in a struct, they are public by default.

18. What is an interface in C++?

a) A class with all member functions defined

b) A class with only pure virtual functions

c) A function that interacts with users

d) A special type of destructor

Answer:

b) A class with only pure virtual functions

Explanation:

An interface in C++ is a class that contains only pure virtual functions. It provides a way to define a contract that derived classes must implement.

19. What is composition in C++?

a) Combining multiple objects into a single class

b) Creating complex functions

c) Including one class within another

d) Writing a function inside another function

Answer:

c) Including one class within another

Explanation:

Composition in C++ is a design principle where one class includes objects of another class as its members, representing a 'has-a' relationship.

20. What is the significance of the 'public', 'private', and 'protected' access specifiers in C++?

a) They define the scope of functions

b) They determine the inheritance type

c) They control access to class members

d) They specify the lifetime of class members

Answer:

c) They control access to class members

Explanation:

The 'public', 'private', and 'protected' access specifiers in C++ determine the accessibility of class members. 'Public' members are accessible everywhere, 'private' members are accessible only within the class, and 'protected' members are accessible in the class and its derived classes.

21. What is the diamond problem in C++?

a) A problem that occurs with multiple inheritance

b) An issue related to operator overloading

c) A problem when using virtual functions

d) An error that occurs when two classes have the same name

Answer:

a) A problem that occurs with multiple inheritance

Explanation:

The diamond problem in C++ is a complication that arises in scenarios of multiple inheritance when a class inherits from two classes that both inherit from a common base class.

22. What is the use of the 'new' operator in C++?

a) To create a new variable

b) To allocate dynamic memory

c) To create a new class

d) To start a new scope

Answer:

b) To allocate dynamic memory

Explanation:

The 'new' operator in C++ is used for dynamic memory allocation. It allocates memory on the heap for a variable or an array and returns a pointer to the allocated memory.

23. What is a friend function in C++?

a) A function that can only be called by another function

b) A member function of a class

c) A function that has access to private and protected members of the class

d) A function that is always static

Answer:

c) A function that has access to private and protected members of the class

Explanation:

A friend function in C++ is a function that is not a member of a class but has access to the class's private and protected members. It is declared using the 'friend' keyword in the class definition.

24. What is a namespace in C++?

a) A feature used for managing global variables

b) A class that contains other classes

c) A container for identifiers to avoid name conflicts

d) A way to group functions

Answer:

c) A container for identifiers to avoid name conflicts

Explanation:

A namespace in C++ is a declarative region that provides a scope to the identifiers (names of types, function, variables, etc.) inside it. Namespaces are used to organize code and prevent name conflicts in large projects.

25. What is exception handling in C++?

a) Handling errors in the program logic

b) A mechanism to handle runtime errors

c) Correcting syntax errors in the code

d) Managing memory allocation errors

Answer:

b) A mechanism to handle runtime errors

Explanation:

Exception handling in C++ is a mechanism that uses try, catch, and throw keywords to handle errors that occur during the execution of a program (runtime errors). It helps in managing unexpected situations in a controlled way.