Programming T.A. Standish Languages Editor Guarded Commands, Nondeterminacy and Formal Derivation of Programs Edsger W. Dijkstra

So-called "guarded commands " are introduced as a building block for alternative and repetitive constructs that allow nondeterministic program components for which at least the activity evoked, but possibly even the final state, is not necessarily uniqilely determined by the initial state. For the formal derivation of programs expressed in terms of these constructs, a calculus will be be shown. Key Words and Phrases: programming languages, sequencing primitives, program semantics, programming language semantics, nondeterminacy, case-construction, repetition, termination, correctness proof, derivation of programs, programming methodolog