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A Step-by-Step Approach to Learn Object Oriented Programming

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  • Difficulty Level : Easy
  • Last Updated : 28 Jan, 2021
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Object-Oriented Programming or OOP’s refers to the language that uses objects in programming. It is primarily concerned with the implementation of real-world entities such as inheritance, polymorphism, etc. in programming. For instance – in the class of Living Things; Humans, Animals, Plants, Microorganism, etc. are known as an object. OOP is used to solve real-world problems. OOP has several additional advantages like faster and easier to execute, provide a clear structure to the program which makes others easier to read the code, it uses the DRY principle “Don’t Repeat Yourself” which makes code easy to maintain modify and debug.

Also, OOP is not only important for Academic Exams but also very crucial in Interviews, especially for Fresher’s Interviews. There are a lot of topics in OOP and in this roadmap, we will discuss all these topics in sequence. If any fresher or Student will follow this Roadmap, he/she will definitely crack the Interview as well as College or University Exams based on OOPs Programming.

1. First Step

Before moving forward for learning OOP’s Concept, one must have basic knowledge about the fundamentals and syntax of C++, Java, Python, or any other relevant programming language. It will help you to implement the OOPs concepts in programming conveniently.

2. Second Step

After that, you must follow the Overview Points of OOP’s concept like:

  • What Is Object-Oriented Programming?
  • Object-Oriented Programming relation with the real world and how real-world problems can be solved by it.
  • Why we Study Object-Oriented Programming and why it is important to learn?
  • Limitations and advantages of OOP
  • Difference between Procedural and Object-Oriented Programming?
  • Why OOP is preferred over Procedural Programming Language?

So, before diving deep into the OOP concepts – one must have knowledge about the above questions. For answers or reference to these one can follow – GeeksforGeeks website or any recommended book. The important books for learning OOP are as follows:

  • For C++ : Object-Oriented Programming with C++ by E.Balagurusamy.
  • For JAVA : Java: The Complete Reference by Herbert Schildt.
  • For Python: Mastering Object-oriented Python Book by Steven F. Lott.

3. Third Step

Now after following the above steps we will move further about the Pillar’s of Object-Oriented Programming Language as follows:

  • What is Class
  • What is Object
  • Difference between Class and Object.
  • Use of Classes and Object Inside and Outside of Main Class.
  • Can Class and Object exist or use Individually?
  • Real-World Analogy Of Class and Object.
  • Access Modifiers (public, private, protected, etc.)
  • Member Function(Inner and Outer class function)

4. Fourth Step

Important Keywords to learn:

  1. Static Keyword
  2. Virtual Keyword
  3. Abstract Keyword
  4. Final Keyword
  5. Explicit keyword
  6. This Keyword
  7. new Keyword
  8. const keyword
  9. super keyword

One must have knowledge about these keywords like their definition, uses, pros, and cons, etc., and why it is important to learn.

5. Fifth Step

Constructor and Destructor :

  • Definition and Working.
  • Rules and Types.
  • Purpose of Using Constructor and Destructor
  • Difference between Constructor and Methods (In Java)
  • Can Constructor Perform Other Task rather than Initialization?
  • Does Constructor Return any value?
  • Constructor vs Destructor.
  • Is there any Constructor Class?

6. Sixth Step

Features of OOPS

Polymorphism: In this, one must know:

  • What is Polymorphism
  • Categories: Function/Operator overloading, Compile time polymorphism, Function overriding, Runtime Polymorphism
  • Which function can be overloaded and which functions can’t be overloaded with explanation
  • Virtual function
  • Dynamic Binding
  • Virtual Class
  • Derived Class
  • Inline Virtual Function
  • Abstract Class
  • Pure virtual function
  • Pure Virtual Destructor
  • Instanceof Operator


  • Subclass
  • Superclass
  • Reusability
  • Need for Inheritance
  • Can OOP exist without Inheritance
  • Inheritance types (Single, Multiple, Hierarchical, Multilevel, Hybrid, Virtual Inheritance)
  • Real-life examples of Inheritance
  • Limitation of Inheritance
  • Sealed Modifier
  • Object Slicing


  • Definition
  • Need
  • How to achieve
  • Real-World Example
  • Packages (In Java)


  • Definition
  • When to use
  • How to Achieve
  • Difference between Inheritance and Abstraction
  • Difference between Encapsulation and Abstraction


  • Dynamic Binding
  • Message Passing
  • Object Cloning
  • Wrapper Class

So there are the important OOPs topics for Interview and Academic Examination which if followed properly will sure get you the success.

Also, these topics must be covered by following the important  principle of learning:

  • Get in-depth knowledge about the topic.
  • Must know Implementation details.
  • How it is related to the real world.

7. Seventh Step

  • Important Interview Questions Of OOP Concept:
  • C vs C++ vs Java vs Python (Just get the idea of how they are different)
  • Difference between Procedural and OOP language?
  • Why Java is not a pure Object-Oriented Programming Language?
  • Is an Array a Primitive type or an Object in Java?
  • What is early and late binding?
  • What is the default access modifier?
  • How many instances can be created for an abstract class?
  • Define Garbage Collection and how does it work?
  • Define Manipulators?
  • What do you mean by Final block?
  • What is the final variable?
  • What do you mean by exception?
  • Is an error basically the same as an exception?
  • It is possible for a class to inherit the constructor of its base class?
  • When Should we use Structure instead of Class?
  • Difference and Similar between Struct and class?
  • Scope Resolution operator
  • What is Deep/Shallow Copy?
  • Copy Constructor vs Assignment Operator
  • Can we have more than one value in class?
  • How destructors are different from normal member function?
  • Difference between new and override?
  • Does Overriding Works with Inheritance?
  • Generalization vs Aggregation vs Composition

Important Object-Oriented Designing:

  • Design a HASH map
  • Design LRU cache
  • Design a call Center
  • Design a Deck of Cards
  • Design a parking lot
  • Design an Online Chat System
  • Design an Address Book
  • Design Bank Management System
  • Design an ATM
  • Design Hotel Management System
  • Design Library Management System

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