Cyrus

Cyrus is a computer chess program originally created by British programmer Richard Lang. Lang began developing it in January 1981, writing the program in assembly language for the Z80 processor. After its success in computer-chess competition, it was commercially developed by Intelligent Software and released in several forms for computers including the ZX Spectrum, Dragon 32, TRS-80 Color Computer and IBM PC. The first commercial versions appeared for 8-bit home computers in 1982, while an expanded IBM PC edition was released for MS-DOS in 1985.

The program allows a human player to compete against the computer in a conventional game of chess. Its various editions provide several playing levels, enabling users to choose between relatively quick responses and deeper calculations. The computer recognizes the standard rules of chess and can play either colour. The presentation differs between platforms, but most versions use a clear overhead board designed primarily for practical play rather than decorative effect.

The DOS edition is more visually elaborate than the early 8-bit conversions and offers both a conventional two-dimensional board and a three-dimensional perspective display. Moves are entered by selecting the starting and destination squares, while additional commands provide access to the program’s playing and analysis functions. Although its graphics are austere when compared with later titles such as The Chessmaster, the uncluttered board keeps the current position easy to examine.

The original tournament version of Cyrus made a remarkable debut at the second European Microcomputer Chess Championship, held at the Personal Computer World Show in London in 1981. Competing against eleven other programs, it won all five of its games and finished as the clear champion. This result established Richard Lang as an important computer-chess programmer. An improved version called Cyrus II appeared at the following European championship in 1982, although Lang later acknowledged that it had been entered before its development and testing were complete.

Cyrus represents the beginning of one of the most successful lineages in commercial computer chess. Lang subsequently developed Psion Chess, whose engine shared first place at the 1984 World Microcomputer Chess Championship. His later programs powered a succession of championship-winning Mephisto chess computers and ultimately led to ChessGenius. The original Cyrus is naturally limited in presentation and playing strength by the hardware for which it was written, but its perfect result in its first major tournament gives it considerable historical importance.