Chess 0.5X

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Chess 0.5X,
a chess program by Wim Elsenaar written in the early 80s at the Vrije Universiteit Amsterdam to run on a PDP-11. Chess 0.5X was an PDP-11 assembly port of Larry Atkin's and Peter W. Frey's didactic Pascal program Chess 0.5, as published 1978 in Byte Magazine including source code listing. Despite many changes and further development, which in fact seemed to qualify for a new entry, the program's name was chosen in dependence to its initial origin, using a Chess 4.0 like structure of a Shannon Type A program with alpha-beta and quiescence search [1].

Tournament Play

Chess 0.5X competed at several early Dutch Open Computer Chess Championships. Already with a strong debut at the DOCCC 1982, it won the DOCCC 1983 and the DOCCC 1984 both with a perfect 100% score. At the International Computer Chess Tournament 1984 in Baarn, Chess 0.5X narrowly missed the tournament win, losing the final round from PK83 which had zero points so far. Winner Merlin was initially based on Chess 0.5 as well [2] [3].

See also



  1. Wim Elsenaar (1983). Chess 0.5X in Peter van Diepen (ed.) (1983). Toernooibulletin van het Nederlands kampioenschap computerschaak 1982. pdf hosted by Hein Veldhuis » DOCCC 1982
  2. Werner DePauli-Schimanovich (2006). Europolis 6. Informatik für Spiele und Verkehr. Extension der Mengenlehre, Herausgeber: Franz Pichler, Universitätsverlag Rudolf Trauner, ISBN 978-3-85487-946-6, (SG7) Merlin (ein ComputerChess-Programm) s. 171 (German), Google Books
  3. Helmut Horacek, Marcus Wagner (1981). Das Schachprogramm Merlin, Verbesserung von Laufzeit-Effizient, Eröffnungsbibliothek und Bewertungsfunktion. 4. Tagung "Berichte aus Informatik-Instituten" (German)

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