Changes

The '''Castling Rights''' specify whether both sides are principally able to [[Castling|castle]] king- or queen side, now or later during the game - whether the involved pieces have already moved or in case of the rooks, were captured. Castling rights do not specify, whether castling is actually possible, but are a pre-condition for both wing castlings. Two [[Bit|bits]] per side are appropriate to store the castling rights, often one uses one [[Nibble|nibble]] to store the rights for both sides inside a [[Chess Position|position]] object, a kind a [[Array|array]] of four booleans.

Two [[Bit|bits]] per side are appropriate to store the castling rights, often one uses one [[Nibble|nibble]] to store the rights for both sides inside a [[Chess Position|position]] object, a kind a [[Array|array]] of four booleans. =Irreversibility=In [[Make Move|make move]] one has to consider that king-moves including castling itself reset both castling bits per side.  Rook-moves from their original [[Squares|square]], or [[Captures|captures]] of rooks on their original squares reset the appropriate castling bits per wing and side. Changed castling rights should be considered in the [[Zobrist Hashing|zobrist key]] of the position, to reflect the irreversibility of the otherwise [[Reversible Moves|reversible move]], concerning [[Repetitions|repetitions]]. On the other hand, changed castling rights don't necessarily reset the [[Halfmove Clock|halfmove clock]] regarding the [[Fifty-move Rule|fifty-move rule]]<ref>[http://www.horst-wandersleben.de/Wette.htm Computerschach - Eine Wette, die ich gerne verloren habe] by [[Horst Wandersleben]] (German)</ref>.

* [http://www.open-aurec.com/wbforum/viewtopic.php?f=4&t=50635 0x88 FRC castle questions] by [[Daniel Uranga]], [[Computer Chess Forums|Winboard Forum]], December 12, 2009 » [[Chess960]]==2010 ...==