The "OBJECT ORIENTED PROGRAMMING IN C++ " book has two primary objectives; to teach the basic principles of object oriented programming as outlined in curricula at many leading universities, and to teach how to implement it. This book has been written for the students of sciences and engineering departments and colleges who aspiring to learn and venture into the world of object oriented programming in C++. The book uses a simple language and presents the subject matter clearly using various examples and exercises with complete OO-codes in C++. Concepts have been explained as much as possible so that the student understands the underlying essentials to the subject matter. The activities and exercises both for class and for lab are listed with the work sheets in the end of each chapter, they are aimed at helping the student re-evaluate what has been studied and covered in the lessons.