This book is concerned with the generic concepts of object Oriented Programming (OOP) and their implementation using common programming languages such as C++ and Java. This book has been written as per syllabi of various universities and the revised syllabus of Anna University for the CSE branch. Though, it has been written as per the syllabus of Anna University, some additional topics have also been covered, which make this book a good reference for OOP in general.The book uses plain and simple language to explain the basics OOP and wherever needed is well supported by a good set of simple and easy to understand examples. The organisation of the book is as follows: 1.Br>chapter 1 explains in detail the concepts involved in OOP in a generic manner I.E. Independent of the programming languages used for implementing them.2. Chapters 2-13 explain the implementation of the OOP concepts using C++. this part of the book statrts with an overview of C++ basics and proceeds right through the various advanced concepts involved in writing object Oriented programs using C++.3. Chapters 14-25, similarly explain the implementation of the OOP concepts using Java.Table of Contents: 1. Object Oriented programming-an introduction, 2. C++ fundamentals, 3. Control flow, 4. Arrays and strings in C++, 5. Functions and pointers, 6. Classes and objects in C++, 7. Inheritance, 8. Virtual functions, 9. Friend function, 10. File handling, 11. Exception handling, 12. Function templates, 13. Namespaces, 14. Overview of Java, 15. Variables and primitive data types, 16. Operators, 17. Control statements, 18. Arrays in Java, 19. Classes, objects and methods, 20. Inheritance, 21. Interfaces and packages, 22. Exception handling, 22. Multithreading, 24. Strings, 25. Input and output.