Chess

Chess is a classic logic board game involving two players. It is played on a chessboard, a square-checkered board with 64 squares arranged in an eight-by-eight grid. At the beginning of the game each player controls sixteen pieces: one king, one queen, two rooks, two knights, two bishops, and eight pawns. The object of the game is to checkmate the opponent's king, whereby the king is under immediate attack (in "check") and there is no way to remove or defend it from attack on the next move.

The game's present form emerged in Europe during the second half of the 15th century, an evolution of an older Indian game, Shatranj. Theoreticians have developed extensive chess strategies and tacticssince the game's inception. Computers have been used for many years to create chess-playing programs, and their abilities and insights have contributed significantly to modern chess theory. One, Deep Blue, was the first machine to beat a reigning World Chess Champion when it defeated Garry Kasparov in 1997.

Matches between individuals took place as early as the 9th century. The tradition of organized competitive chess started during the 16th century. The first official World Chess Champion, Wilhelm Steinitz, claimed his title in 1886; the current World Champion is Viswanathan Anand from India. In addition to the World Championship, there is also the Women's World Championship, the Junior World Championship, the World Senior Championship, the Correspondence Chess World Championship, the World Computer Chess Championship, and Blitz and Rapid World Championships (see fast chess). The Chess Olympiadis a popular competition among teams from different nations. Online chess has opened amateur and professional competition to a wide and varied group of players.

Chess is a recognized sport of the International Olympic Committee and international chess competition is sanctioned by the FIDE. Today, chess is one of the world's most popular games, played by millions of people worldwide at home, in clubs, online, by correspondence, and in tournaments. Some other popular forms of chess are fast chess and computer chess. There are also many chess variants which have different rules, different pieces, different boards, etc.

The pieces are divided, by convention, into white and black sets. The players are referred to as "White" and "Black", and each begins the game with sixteenpieces of the specified color. These consist of one king, one queen, two rooks, two bishops, two knights and eight pawns.

Movement
White always moves first. After the initial move, the players alternately move one piece at a time (with the exception of castling, when two pieces are moved). Pieces are moved to either an unoccupied square, or one occupied by an opponent's piece, capturing it and removing it from play. With the sole exception of en passant, all pieces capture opponent's pieces by moving to the square that the opponent's piece occupies.

Each chess piece has its own style of moving. A player may not make any move which would put or leave his king under attack. If the player to move has no legal moves, the game is over; it is either a checkmate - if the king is under attack - or a stalemate - if the king is not.
 * The king moves one square in any direction, the king has also a special move which is called castling and also involves a rook.
 * The rook can move any number of squares along any rank or file, but may not leap over other pieces. Along with the king, the rook is also involved during the king's castling move.
 * The bishop can move any number of squares diagonally, but may not leap over other pieces.
 * The queen combines the power of the rook and bishop and can move any number of squares along rank, file, or diagonal, but it may not leap over other pieces.
 * The knight moves to any of the closest squares which are not on the same rank, file or diagonal, thus the move forms an "L"-shape two squares long and one square wide. The knight is the only piece whichcan leap over other pieces.
 * The pawn may move forward to the unoccupied square immediately in front of it on the same file, or on its first move it may advance two squares along the same file provided both squares are unoccupied, or it may move to a square occupied by an opponent’s piece, which is diagonally in front of it on an adjacent file, capturing that piece. The pawn has two special moves, the en passant capture, and pawn promotion.


 * Pawns can optionally move two squares forward instead of one on their first move only. They capture diagonally (black x's); they cannot capture with their normal move (black circles). Pawns are also involved in the special move en passant (below).

Castling
&nbsp Examples of castlingMain article: Castling Once in every game, each king is allowed to make a special move, known as castling. Castling consists of moving the king two squares along the first rank toward a rook (which is on the player’s first rank) and then placing the rook to the last square the king has just crossed. Castling is only permissible if all of the following conditions hold: It is a common mistake to think that the requirements for castling are more stringent than noted above. In particular, Finally, as with any move, castling is illegal if it would place the king in check.
 * Neither of the pieces involved in the castling may have been previously moved during the game;
 * There must be no pieces between the king and the rook;
 * The king may not currently be in check, nor may the king pass through squares that are under attack by enemy pieces.
 * The rook which is involved in the castling may be under attack.
 * In queenside castling, the square next to the rook may be under attack.

En passant
&nbsp Examples of pawn moves: promotion (left) and en passant (right)Main article: En passant When a pawn advances two squares and there is an opponent's pawn on an adjacent file next to its destination square, then the opponent's pawn can capture it en passant (in passing), and move to the square the pawn passed over. However, this can only be done on the very next move, or the right to do so is lost. For example, if the black pawn has just advanced two squares from g7 to g5, then the white pawn on f5 can take it via en passant on g6 (but only on white's next move).Main article: Promotion (chess) When a pawn advances to the eighth rank, as a part of the move it is promoted and must be exchanged for the player's choice of queen, rook, bishop, or knight of the same color. Usually, the pawn is chosen to be promoted to a queen, but in some cases another piece is chosen, called underpromotion. In the diagram on the right, the pawn on c7 can be advanced to the eighth rank and be promoted to an allowed piece. There is no restriction placed on the piece that is chosen on promotion, so it is possible to have more pieces of the same type than at the start of the game (for example, two queens).

Check
&nbsp Main article: Check (chess) When a king is under immediate attack by one or two of the opponent's pieces, it is said to be in check. A response to a check is a legal move if it results in a position where the king is no longer under direct attack (i.e. not in check). This can involve capturing the checking piece, interposing a piece between the checking piece and the king (which is possible only if the attacking piece is a queen, rook, or bishop and there is a square between it and the king), or moving the king to a square where it is not under attack. Castling is not a permissible response to a check. The object of the game is to checkmate the opponent; this occurs when the opponent's king is in check, and there is no legal way to remove it from attack. ==

End of the game
Although the objective of the game is to checkmate the opponent, chess games do not have to end in checkmate—either player may resign if the situation looks hopeless. It is considered bad etiquette to continue playing when in a truly hopeless position. If it is a timed game a player may run out of time and lose, even with a much superior position. Games also may end in a draw (tie). A draw can occur in several situations, including draw by agreement, stalemate, threefold repetition of a position, the fifty-move rule, or a draw by impossibility of checkmate (usually because of insufficient material to checkmate). As checkmate from some positions cannot be forced in less than 50 moves (see e.g. pawnless chess endgame and two knights endgame), the fifty-move rule is not applied everywhere,[6] particularly in correspondence chess.