Object-oriented programming is a popular buzzword these days. What is the reason for this popularity? Is object-oriented programming the solution to the software crisis or is it just a fad? Is it a simple evolutionary step or a radical change in software methodology? What is the central idea behind object-orien­ ted design? Are there special applications for which object-oriented program­ ming is particularly suited? Which object-oriented language should be used? There is no simple answer to these questions. Although object-oriented programming was invented more than twenty years ago, we still cannot claim that we know everything about this programming technique. Many new con­ cepts have been developed during the past decade, and new applications and implications of object-oriented programming are constantly being discovered. This book can only try to explain the nature of object-oriented program­ ming in as much detail as possible. It should serve three purposes. First, it is intended as an introduction to the basic concepts of object-oriented program­ ming. Second, the book describes the concept of prototypes and explains why and how they can improve the way in which object-oriented programs are developed. Third, it introduces the programming language Omega, an object­ oriented language that was designed with easy, safe and efficient software development in mind.