Top OOPS Interview Questions and Answers (2025)

OOPS Interview Questions for Fresher

OOPs, abbreviated as Object-oriented programming, are considered a collection of objects that are instances of classes to design and organize code. They revolve around the concepts of Data abstraction, Inheritance, Encapsulation, and polymorphism.

1. How to Explain OOP?

Object-Oriented Programming (OOP) is a programming model that organizes the code using objects that bundle data and behaviour together. It organizes the code using objects, which are similar to real-world things that bundle the data (or attributes) and behavior (or methods) together.

2. Who invented OOP?

Ole-Johan Dahl and Kristen Nygaard invented OOP in the Simula language, and they are the pioneers of Object-Oriented Programming. They developed it in the 1960s while working at the Norwegian Computing Center. 

3. Why is OOPS important?

OOPS is important. It helps to write better, maintainable, and scalable code. OOP is important for the following reasons

• Real-World Modeling
• Reusability (via Inheritance)
• Maintainability (Encapsulation)
• Flexibility (Polymorphism)
• Modularity
• Easier Testing and Debugging
• Popular and Widely Used

4. What are the benefits of OOP?

• Inheritance can eliminate redundant code and extend the use of existing classes
• The complexity of software can be easily managed
• Based on objects, it is easy to partition the work in a project.
• OOPs can easily be upgraded from small to large systems.
• The principle of data hiding helps programmers to build secure programs. 
• It helps to save development time and higher Authority
• New data and functions can be easily added
• The principle of data hiding helps build secure programs that can't be invaded by code in other parts of the program.
• Object-oriented systems are easy to upgrade.

5. What are the basic key principles of OOP?

The basic principles of OOP include

• Classes
• Objects
• Data Abstraction
• Encapsulation
• Inheritance
• Polymorphism
• Message passing
• Dynamic binding

6. What is the need for OOP?

The major motivation factor in the invention of object oriented approach is to overcome the following problems and some of the flaws encountered in the procedure-oriented approach. The problems are:

• To design a system with an open interface.
• To manage time schedule.
• To improve the quality of the software.
• To ensure the reusability and extensibility of modules.
• To represent real-life entities of problems in system design.
• To improve software productivity and decrease cost.
• To industrialize the software development process
• To develop modules that are tolerant to any changes in the future

7. What is Data Abstraction?

• Data Abstraction refers to the act of representing essential features without including the background explanation or the details. Classes use the concept of Abstraction.
• Abstraction means showing only the required things and hiding the background details.

8. What is Data Encapsulation?

• Wrapping of Data members and member functions into a single unit (called a class) is known as Encapsulation. Access modifiers (Like Private, Public, and Protected ) restrict direct access to some components. 

9. What are the benefits of OOP?

•     Inheritance can eliminate redundant code and extend the use of existing classes.
•     The complexity of software can be easily managed
•     It is easy to partition the work in a project based on objects.
•     OOPs can easily be upgraded from small to large systems.
•     The principle of data hiding helps programmers build secure programs. 
•     It helps to save development time and higher Authority
•     New data and functions can be easily added
•     The principle of data hiding helps build secure programs that cannot be invaded by code in other parts of the program.
•     Object-oriented systems are easy to upgrade.

10. What are the basic principles of OOP?

The basic principles of the class include

• Classes
• Objects
• Data Abstraction
• Encapsulation
• Inheritance
• Polymorphism
• Message Passing
• Dynamic binding

11. What is the difference between Procedure Oriented Programming and Object Oriented Programming?

12. What are the most popular OOP Programming Languages?

The most popular object-oriented programming languages include:

• C++
• Java.
• Smalltalk
• Ruby
• Delphi
• Simula.
• Charm++
• Eiffel.

12. What are the Applications of OOP?

The promising application of OOP includes:

• Object-oriented databases.
• Real–Time systems
• AI and expert systems.
• Neural networks and parallel programming.
• CIM/CAM/CAD system.
• Simulation and modeling
• Decision support and office automation systems.
• Hypertext, hypermedia, and expertext.
• Image Processing
• Computer-Aided Teaching
• Distributed Computing and Applications
• Computer-Assisted Concurrent Engineering
• Data Warehouse and Data Mining
• Parallel Computing
• Enterprise Resource Planning
• Database Management Systems
• Web-based Applications
• Component-based Applications
• Data security and management
• Pattern Recognition
• Mobile Computing
• Computer-Aided Design and Manufacturing
• Intelligent Systems
• Business Process Re-engineering

13. Can a class inherit multiple classes? 

It depends on Programming languages. C++, Python support multiple Inheritance. While PHP, C#, and Java do not support multiple class Inheritance. This is to avoid complexity and ambiguity.

OOPS Quiz Questions and Answers