Colossus Chess is a series of chess-playing computer programs developed by Martin Bryant, commercially available for various home computers in the 1980s.
Colossus Chess 4.0 on Commodore 64
Bryant started Colossus Chess in 1983, using his White Knight Mk 11 program, winner of the 1983 European Microcomputer Chess Championship, as a basis. It was developed on an Apple II, but was first commercially released for Commodore 64 as Colossus Chess 2.0 (CDS Micro Systems, 1984). A number of releases for 8-bit microcomputers followed. Version 3.0 was released in 1984 for the Atari 8-bit family of computers (published by English Software), followed by 4.0 in 1985 which was released on most formats of the day (published by CDS).
Colossus Chess 4.0 on Commodore 64 (3D chessboard)
Colossus Chess featured time-controlled play with game clocks, an opening book with 3,000 positions, and problem-solving mode that could solve normal mates, selfmates and helpmates. Pondering on opponent's time and a three-dimensional chessboard were introduced in Colossus Chess 4.0. All releases were written in the assembly language of the appropriate CPU; the ZX Spectrum version could examine an average of 170 positions per second.
Uncommon for microcomputer chess programs of the era, Colossus had a full implementation of the rules of chess, including underpromotion, the fifty-move rule, draw by repetition, and draw by insufficient material. Colossus was also able to execute all the basic checkmates, including the difficult bishop and knight checkmate.
Colossus Chess X
The program was subsequently ported to Atari ST (1988), Amiga (1989) and IBM PC (1990) under the title Colossus Chess X. The new releases featured four chess sets and enhanced graphics developed with the assistance of Gary Thomlinson and Carl Cropley. The opening book was extended to 11,000 positions, and the program had the ability to learn from past playing experiences.
Colossus Chess X on PC
No work was done on Colossus Chess from 1991 to 2005, when Martin Bryant created a completely new and freely available Windows version conforming to the Universal Chess Interface. It was written in C#, then converted to C for speed, and was finally publicly released in 2006. , the latest version is 2008b.