On the use of transition diagrams in the design of a user interface for an interactive computer system

This paper deals with what might be called the top level design of an interactive computer system. It examines some problems which arise in trying to specify what the user interface of such a system should be. It proposes a concept—the terminal state—and a notation—the terminal state transition diagram—which make the design of the top level somewhat easier. It also proposes a user interface in which the notion of terminal state is explicit. This user interface seems to provide a great improvement in flexibility and case of adding subsystems to a general purpose system.