Top 40 OOPs Interview Questions and Answers for 2024

Object-Oriented Programming (OOPs) is a fundamental concept in the world of programming, and almost every interview you attend will require you to have a solid understanding of this concept. In this comprehensive article, we will explore the top 40 OOPs interview questions and provide detailed answers to help you ace your interviews.

Table of Contents

1. Basic OOPs Interview Questions
2. Advanced OOPs Interview Questions
3. OOPs Coding Problems
4. OOPs MCQs

Basic OOPs Interview Questions

1. What is meant by the term OOPs?
   OOPs stands for Object-Oriented Programming. It is a programming paradigm based on objects, which can be considered as real-world instances of entities that have characteristics (data) and behaviors (methods).

2. What is the need for OOPs?
   There are several reasons why OOPs is preferred:

   • It helps users understand the software easily, even if they don’t know the actual implementation.
   • OOPs increases the readability, understandability, and maintainability of the code.
   • Even very large software can be easily written and managed using OOPs.

3. What are some major Object-Oriented Programming languages?
   Some of the major Object-Oriented Programming languages include Java, C++, JavaScript, Python, PHP, and many others.

4. What are some other programming paradigms other than OOPs?
   Other programming paradigms include:

   • Imperative Programming Paradigm (Procedural Programming, Parallel Programming)
   • Declarative Programming Paradigm (Logical Programming, Functional Programming, Database Programming)

5. What is meant by Structured Programming?
   Structured Programming refers to the method of programming that consists of a completely structured control flow. It contains a set of rules and has a definitive control flow, such as (if/then/else), (while and for), block structures, and subroutines. Nearly all programming paradigms, including OOPs, include Structured Programming.

6. What are the main features of OOPs?
   The main features of OOPs are:

   • Inheritance
   • Encapsulation
   • Polymorphism
   • Data Abstraction

7. What are some advantages of using OOPs?
   Some advantages of using OOPs include:

   • It helps in solving complex problems.
   • Highly complex programs can be created, handled, and maintained easily.
   • OOPs promotes code reuse, thereby reducing redundancy.
   • It helps to hide unnecessary details with the help of Data Abstraction.
   • OOPs is based on a bottom-up approach, unlike Structural Programming, which uses a top-down approach.
   • Polymorphism offers a lot of flexibility.

8. Why is OOPs so popular?
   OOPs is popular because it helps in writing complex code easily and allows users to handle and maintain it efficiently. Additionally, the main pillars of OOPs (Data Abstraction, Encapsulation, Inheritance, and Polymorphism) make it easy for programmers to solve complex scenarios.

Advanced OOPs Interview Questions

1. What is a class?
   A class is a template or blueprint that contains values (member data or members) and a set of rules (behaviors or functions). When an object is created, it automatically takes the data and functions defined in the class. The class is essentially a blueprint for objects, and you can create as many objects as you want based on a class.

2. What is an object?
   An object refers to an instance of a class, which contains instances of the members and behaviors defined in the class template. In the real world, an object is an actual entity with which the user interacts, whereas a class is just the blueprint for that object. Objects consume memory space and have specific characteristics and behaviors.

3. What is encapsulation?
   Encapsulation is the process of binding data members and methods of a program together into a single unit, without revealing unnecessary details. It can also be defined in two ways:

   • Data hiding: Encapsulation is the process of restricting access to any member of an object.
   • Data binding: Encapsulation is the process of binding the data members and methods together as a whole, as a class.

4. What is polymorphism?
   Polymorphism refers to the ability of an entity (code, data, method, or object) to behave differently under different circumstances or contexts. There are two types of polymorphism in OOPs languages: Compile-time polymorphism and Runtime polymorphism.

5. What is Compile-time Polymorphism and how is it different from Runtime Polymorphism?

   • Compile-time Polymorphism (Static Polymorphism): Compile-time polymorphism, also known as Static Polymorphism, refers to the type of polymorphism that happens at compile time. The compiler decides what shape or value the entity should take. Method overloading is an example of compile-time polymorphism.
   • Runtime Polymorphism (Dynamic Polymorphism): Runtime polymorphism, also known as Dynamic Polymorphism, refers to the type of polymorphism that is resolved during runtime. The actual implementation of the function is decided during the execution. Method overriding is an example of runtime polymorphism.

6. How does C++ support Polymorphism?
   C++ supports both Compile-time and Runtime Polymorphism:

   • Compile-time Polymorphism: C++ supports compile-time polymorphism with the