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Philosophical Magazine, Ser.7, Vol. 41, No. 314 - March 1950.

XXII. Programming a Computer for Playing Chess1
By CLAUDE E. SHANNON Bell Telephone Laboratories, Inc., Murray Hill, N.J.2 [Received November 8, 1949]

1. INTRODUCTION This paper is concerned with the problem of constructing a computing routine or "program" for a modern general purpose computer which will enable it to play chess.Although perhaps of no practical importance, the question is of theoretical interest, and it is hoped that a satisfactory solution of this problem will act as a wedge in attacking other problems of a similar nature and of greater significance. Some possibilities in this direction are: (1)Machines for designing filters, equalizers, etc. (2)Machines for designing relay and switching circuits.(3)Machines which will handle routing of telephone calls based on the individual circumstances rather than by fixed patterns. (4)Machines for performing symbolic (non-numerical) mathematical operations. (5)Machines capable of translating from one language to another. (6)Machines for making strategic decisions in simplified military operations. (7)Machines capable of orchestrating a melody. (8)Machinescapable of logical deduction. It is believed that all of these and many other devices of a similar nature are possible developments in the immediate future. The techniques developed for modern electronic and relay type computers make them not only theoretical possibilities, but in several cases worthy of serious consideration from the economic point of view. Machines of this general type are anextension over the ordinary use of numerical computers in several ways. First, the entities dealt with are not primarily numbers, but rather chess positions, circuits, mathematical expressions, words, etc. Second, the proper procedure involves general principles, something of the nature of judgement, and considerable trial and error, rather than a strict, unalterable computing process. Finally, thesolutions of these problems are not merely right or wrong but have a continuous range of "quality" from the best down to the worst. We might be satisfied with a machine that designed good filters even though they were not always the best possible. 1 First presented at the National IRE Convention, March 9, 1949, NewYork, U.S.A. 2 Communicated by the Author

The chess machine is an ideal one tostart with, since: (1) the problem is sharply defined both in allowed operations (the moves) and in the ultimate goal (checkmate); (2) it is neither so simple as to be trivial nor too difficult for satisfactory solution; (3) chess is generally considered to require "thinking" for skilful play; a solution of this problem will force us either to admit the possibility of a mechanized thinking or tofurther restrict our concept of "thinking"; (4) the discrete structure of chess fits well into the digital nature of modern computers. There is already a considerable literature on the subject of chess-playing machines. During the late 19th century, the Maelzel Chess Automaton, a device invented by Von Kempelen, was exhibited widely as a chess-playing machine. A number of papers appeared at thetime, including an analytical essay by Edgar Allan Poe (entitled Maelzel's Chess Player) purporting to explain its operation. Most of the writers concluded, quite correctly, that the Automaton was operated by a concealed human chess-master; the arguments leading to this conclusion, however, were frequently fallacious. Poe assumes, for example, that it is as easy to design a machine which willinvariably win as one which wins occasionally, and argues that since the Automaton was not invincible it was therefore operated by a human, a clear 'non sequitur'. For a complete account of the history of the method of operation of the Automaton, the reader is referred to a series of articles by Harkness and Battell in Chess Review, 1947. A more honest attempt to design a chess-playing machine was made...