The Design of Edison

This paper describes the considerations behind the design of the programming language Edison (Brinch Hansen 1981). Edison is deeply influenced by the advances made by Pascal (Wirth 1971) and its successors Concurrent Pascal (Brinch Hansen 1975) and Modula (Wirth 1977). In my attempt to learn from these previous efforts and improve on them I had to focus on both the virtues and defects of these languages. The criticism may appear very unfair coming from a programmer who has benefited immensely from the innovations of Pascal ten years ago. But such criticism is necessary to gain a clearer perspective of a programming tradition that has become so natural to me that it inhibits my ability to search for better methods. In designing the programming language Edison I tried to do two things: (1) to achieve simplicity by questioning the necessity of a number of wellknown language concepts, and (2) to gain new insight by deliberately approaching language design with a philosophy that is completely different from the spirit in which Concurrent Pascal was designed. The first viewpoint gradually led to the omission of many language features that I had previously thought were valuable features of the programming languages Pascal and Concurrent Pascal, namely