Programming Notation in Systems Design

function of programming notation in systems design and the characteristics of a suitable language are discussed. A brief introduction i s given to a particular language (developed by the author and detailed elsewhere) which has many of the desired properties. Application of the language i s illustrated by the use of familiar examples. In any area of design, systematic design procedures are necessarily based upon methods for the precise and formal description of the entities being designed. Because complex systems commonly embrace elements from a number of disparate disciplines (e.g., computers, programming systems, servomechanisms, accounting systems), there exists no common terminology or notation adequate for the description of an entire complex system, and hence no adequate basis for systematic " systems design ". Despite the variety in the components involved, there is an important element common to all systems design; namely, the universal concern with the procedures or algorithms executed by the system. In a fully automatic system the procedures are, by definition, explicit, and the behavior of such a system can be fully described by the explicit procedures, more commonly called programs. Even in semi-automatic systems a program description can be used effectively to describe the automatic portion and to isolate and identify the variables subject to specification by people or other incompletely predictable agents. The programming notation or language used in the description of a system must be universal enough to conveniently describe programs appropriate to each of the elements embraced in a system. It must also be precise. To be truly effective in design it must further be concise and subject to formal manipulation, i.e., statements in the language must satisfy a good many significant formal identities.