This is a book on object-oriented programming and the BETA programming language. Object-oriented programming originated with the Simula languages developed at the Norwegian Computing Center, Oslo, in the 1960s. The first Simula language, Simula I, was intended for writing simulation programs. Simula I was later used as a basis for defining a general purpose programming language, Simula 67. In addition to being a programming language, Simula1 was also designed as a language for describing and communicating about systems in general. Simula has been used by a relatively small community for many years, although it has had a major impact on research in computer science. The real breakthrough for object-oriented programming came with the development of Smalltalk. Since then, a large number of programming languages based on Simula concepts have appeared. C++ is the language that has had the greatest influence on the use of object-oriented programming in industry. Object-oriented programming has also been the subject of intensive research, resulting in a large number of important contributions.
The authors of this book, together with Bent Bruun Kristensen, have been involved in the BETA project since 1975, the aim of which is to develop concepts, constructs and tools for programming. The BETA language is one main result of this project, the various stages of which have been described in many different reports and articles (Kristensen et al., 1976; 1983a,b; 1985; 1987a,b; 1988; Madsen, 1987; Madsen and Møller-Pedersen, 1988; 1989a,b; 1992; Madsen et al., 1983). This book contains a description of the BETA language together with the conceptual framework on which BETA has been based.