Henry C. Thacher

In using ALGOL, or any other common language for communicating among computers with different input-output media, one or more human beings is normally present in the communication channel. In the otherwise convenient method of communication by published algorithms, at least three humans are directly involved: a typist to prepare the manuscript in reference or publication language, a typesetter, and a keypunch operator to prepare the program for the computer in its hardware language. In spite of checking by authors, proof readers, editors, and verifiers, this process is a noisy one, involving as it does not only copying a synthetic (and therefore unfamiliar) language, but also translation to and from the publication dialect. The number of minor typographical errors which have been detected and reported in published algorithms confirms this observation. Clearly some check of the accuracy with which an algorithm has been transmitted through this noisy channel would be desirable. The solution which we propose is directed particularly to ALGOL 60, but the same problems exist with other common languages, and the principles which we use could be readily adapted to them.