Changes

The square centric classical approach with bitboards was used in [[Chess (Program)|Chess 4.5]] and descibed by [[Larry Atkin]] and [[David Slate]] <ref>[[David Slate]] and , [[Larry Atkin]] ('''1977'''). ''CHESS 4.5 - The Northwestern University Chess Program.'' [[Chess Skill in Man and Machine]] (ed. [[Peter W. Frey]]), pp. 82-118. Springer-Verlag, New York, N.Y. 2nd ed. 1983. ISBN 0-387-90815-3. Reprinted ('''1988''') in [[Computer Chess Compendium]]</ref> . The incrementally updated attack tables, from which most move generation is done, are called ''ATKFR'' and ''ATKTO''. ''ATKFR'' is a set of 64 bitboards which give, for each square, all the squares attacked by the piece, if any, that resides on the square. ''ATKTO'' ([[Square Attacked By]]) is the transpose of ''ATKFR'', giving for each square, the locations of all pieces that attack that square. For instance the square E4 (T) is attacked by a black rook at E8, a black knight at F6, and defended by a white rook at E1 and a white pawn at D3 <ref>[http://www.craftychess.com/hyatt/bitmaps.html Rotated bitmaps, a new twist on an old idea] by [[Robert Hyatt]]</ref> :