Our Program Notation and Its Semantics

Abstract

Since in this monograph we will be studying the design of concurrently executed sequential programs, we need a notation for sequential programs in the first place. At this point we have made a very traditional choice by adopting Dijkstra’s Guarded Command Language, which was first defined in [Dij76]. Its distinguishing features are notational and mathematical austerity, and the incorporation of nondeterminacy in sequential programs. In our study of multiprogramming, nondeterminacy will hardly play a rôle, but mathematical austerity will do so all the more. We will briefly describe this program notation, which we expect to offer no problem to anyone familiar with ALGOL60, Pascal, or even C. We will discuss its semantics in more detail, anticipating in our discussion that in later chapters sequential programs will be considered in cooperation with other ones rather than in isolation.