Pactolus: A Simulator Language Which Makes a Digital Computer Feel Like an Analog Computer (sorta kinda)

Abstract

In the last 10 years over a dozen block-oriented sim ulation languages have been developed for general- purpose digital computers. Several of these succeeded rather well in the semantics aspect of the problem. Almost without exception, however, they failed to provide the human operator with the operational flexibility which is the forte of the analog computer. In the opinion of the author, digital simulation has a most promising future. Unfortunately, at present it seems “stuck dead-center,” and will probably remain so until we achieve a much greater measure of man- machine intimacy. PACTOLUS is an attempt to make a small, general-purpose digital computer not only act but, more importantly, feel like an analog com puter. Alas, it can't be called an unqualified success; it is hopefully a step in the right direction. PACTOLUS is a digital analog simulator program developed for the IBM 1620. Plotter, typewriter, and sense switches are combined to provide a flexible modus operandi. The configuration, initial condi tions, and parameters of the simulation are simply and conveniently specified and may be varied at will. The operator may monitor the results as they are being plotted and interrupt the run if the results suggest a change in the specifications. Variables of secondary interest are recorded at specified time intervals by the typewriter. The program includes all standard analog computer elements plus many spe cial circuit elements: e.g., bang-bang, absolute value, clipper, pulse generator, and zero-order hold. © 1964, The Scottish Medical Journal. All rights reserved.