This textbook is intended for the novice as well as for the experienced programmer who wants to learn more about object-oriented programming. There are three main topics covered in this book. First, it contains a comprehensive introduction to the principles of OOP. Second, it describes prototypes as a vehicle for the construction of object-oriented programs and third, it introduces the new programming language Omega. Omega has been developed by the author as a type-safe object-oriented language and is targeted at easy, safe and efficient software construction. The reader is expected to have sufficient experience with structured and modular programming, as these techniques constitute the foundation on which the object-oriented principles are based.