--- /dev/null
+
+
+
+
+
+ ABSTRACT
+ --------
+
+ CHEKMO-II is a chess playing program which will run on any PDP-8
+ computer. The program will play either the White pieces or the Black
+ pieces and will play and accept all classes of legal moves, including,
+ castling both short and long, en-passant pawn captures, and pawn pro-
+ moting moves to any legal promotion piece. The program prints out its
+ moves in Algebraic Notation, and accepts moves using this Notation.
+
+ Included in the command structure of the program are commands which
+ allow you to input board positions using Forsyth Notation, and get a
+ printout of the board at your terminal.
+
+ EQUIPMENT
+ ---------
+
+ CHEKMO-II will run on any PDP-8 family computer with a minimum of 4K
+ of memory and an ASR33 Teletype (1), or equivalent terminal.
+
+ EXECUTION TIME
+ --------------
+
+ The time that CHEKMO-II takes to calculate a move is highly dependent
+ upon the position of the pieces, but it is generally within the range
+ of 20 seconds to 2 minutes per move. In "blitz mode" (see the "BM"
+ command), CHEKMO-II makes its moves much more quickly, but at the cost
+ of reduced playing strength.
+
+ Note: All times quoted are assuming that CHEKMO-II is being run on
+ a PDP-8/e (1.2 us cycle time).
+
+ LOADING AND STARTING CHEKMO-II
+ ------- --- -------- ---------
+
+ The CHEKMO-II binary tape is a standard binary tape and can be loaded
+ using the BIN Loader program (DEC-08-LBAA-PM), or the OS/8 "ABSLDR"
+ program. The starting address for CHEKMO-II is 0200. CHEKMO-II can
+ be halted and restarted at location 0200 at any time.
+
+
+ (Note for OS/8 users: A short patch to the input routine is available
+ which allows CHEKMO-II to respond to CTRL/C (^C) by returning to the
+ monitor system. Play may be resumed simply by typing ".ST" followed
+ by a carriage return. Specify '/S' to ABSLDR to include this patch.)
+
+
+
+
+ (1) Teletype is a registered trademark of the Teletype Corporation.
+\f
+
+ CHEKMO-II Chess Program for the PDP-8 Page 2
+
+
+
+
+ ON LINE OPERATION
+ -- ---- ---------
+
+ Before continuing please note that all lines of input to CHEKMO-II
+ must be terminated with a carriage return. Typing a CTRL/U character.
+ echos "^U" and erases anything typed so far on a line. Typing a RUBOUT
+ character deletes the last character typed and prints a "\" character
+ to indicate the deletion. CHEKMO-II has an input buffer with room for
+ 24 characters. If more than 24 characters are typed on a line (exclud-
+ ing rubouts and the "rubbed out" characters), a "^U" is printed and the
+ entire line is deleted.
+
+ When CHEKMO-II is started at location 0200 it will print. . .
+
+ CHEKMO-II
+
+ To identify itself and setup the pieces on its internal board to their
+ original squares. Then it will ask. . .
+
+ W. YOUR MOVE?
+
+ The "W. " at the beginning of the line is to indicate that it is whites
+ move. The "YOUR MOVE?" indicates that CHEKMO-II is waiting for you to
+ input a move for white, using modified Algebraic Notation (described on
+ P. 6). If the move that you type in is illegal or impossible CHEKMO-II
+ responds with. . .
+
+ ?
+ W. YOUR MOVE?
+
+ asking again for you to type in a legal move. If a legal move is typed
+ CHEKMO-II will make the move on its internal board, then ask. . .
+
+ B. YOUR MOVE?
+
+ CHEKMO-II is now waiting for you to type in a move for black (note the
+ "B."). As before, typing in an impossible move causes CHEKMO-II to...
+
+ ?
+ B. YOUR MOVE?
+
+ ask again for a legal move. A legal move causes CHEKMO-II to make that
+ move on its internal board, then ask for a move for white.
+\f
+
+ CHEKMO-II Chess Program for the PDP-8 Page 3
+
+
+
+ Play continues in this manner until a move is made that checkmates or
+ stalemates. At that time CHEKMO-II will print. . .
+
+
+ CHECKMATE
+
+ or
+
+ STALEMATE
+
+
+ In either case the final position is then printed
+
+ -- ** -- BK -- ** -- **
+ ** -- ** WQ ** -- ** --
+ -- ** -- ** WK ** -- **
+ ** -- ** -- ** -- ** --
+ -- ** -- ** -- ** -- **
+ ** -- ** -- ** -- ** --
+ -- ** -- ** -- ** -- **
+ ** -- ** -- ** -- ** --
+
+ CHEKMO-II now restarts itself at location 0200 and is ready to play
+ another game.
+
+
+
+ Codes: B- BLACK
+ W- WHITE
+ P- PAWN
+ B- BISHOP
+ R- ROOK
+ Q- QUEEN
+ K- KING
+ N- KNIGHT
+ S- ALSO A KNIGHT
+\f
+
+ CHEKMO-II Chess Program for the PDP-8 Page 4
+
+ SPECIAL COMMANDS
+ ------- --------
+
+ Whenever CHEKMO-II is waiting for you to type in a move, you may
+ instead type in one of the 10 special commands currently implemented.
+ Each special command consists of 2 characters and is described below:
+
+ PW -- CHEKMO-II is instructed to play the white peices. Whenever it
+ is whites turn to move CHEKMO-II will printout and make a move
+ for white instead of asking "YOUR MOVE?"
+
+ PB -- Same as "PW" except that CHEKMO-II makes a move for the black
+ pieces every time it is blacks turn to move.
+
+ PN -- CHECKMO-II plays neither white nor black. This cancels previous
+ "PW" and "PB" commands.
+
+ BD -- CHEKMO-II will print out the current board position.
+
+ MV -- Causes CHEKMO-II to printout and make the next move for the side
+ whose turn it is.
+
+ SK -- Skip the move that CHEKMO-II is asking for, and make it the other
+ sides move.
+
+ Note: According to the laws of chess, "The 2 players must alter-
+ nate in making 1 move at a time". The SK command is included be-
+ cause it can sometimes be fun to use in "non-serious" games.
+
+ RE -- Stands for "Reset" (or "Resign"). It resets CHEKMO-II's internal
+ board to the initial starting position and begins a new game.
+
+ BM -- Puts CHEKMO-II into "Blitz mode". In Blitz mode, CHEKMO-II does
+ not think very deeply about its moves, but instead, makes them in
+ 3 seconds each on the average.
+
+ TM -- Resets CHEKMO-II to its regular "thoughtful" mode of play.
+
+ IP -- Instructs CHEKMO-II to accept the input of a position using For-
+ syth notation (described on Pg. 6) CHEKMO-II prints a ">" to in-
+ dicate that it is ready for you to enter a line. If you violate
+ the rules of Forsyth notation, an error message is printed, and
+ CHEKMO-II waits for you to enter the error line again. If you en-
+ ter in a good line, CHEKMO-II prints a ">" and waits for the next
+ line. When all 8 ranks are entered successfully, the board posi-
+ tion just input gets printed out. Possible error messages and
+ their causes are described below:
+
+ Message Cause
+
+ 1? More than 8 squares specified
+ 2? Less than 8 squares specified
+ 3? Piece color not "W" or "B"
+ 4? Unknown piece letter
+\f
+
+ CHEKMO-II Chess Program for the PDP-8 Page 5
+
+ ALGEBRAIC NOTATION
+ ---------- -------
+
+ Algebraic Notation is the system recommended by the International
+ Chess Federation (F.I.D.E), for the recording of chess moves. Since
+ in regular Algebraic Notation, both upper and lower case letters are
+ used, and since most teleprinters output only upper case letters,
+ CHEKMO-II uses a modified form of algebraic notation to accept moves,
+ and to print out its own moves. This modified Algebraic Notation is
+ described here.
+
+ The ranks (horizontal rows of squares) are numbered from 1 to 8 start-
+ ing from whites side of the board. The files (vertical rows of squares)
+ are numbered from A to H starting at the left (blacks right) hand side
+ of the board. The intersection of the file letter and rank number
+ gives each square a unique name, for example, in the initial position,
+ whites king occupies square E1, blacks king occupies square E8, and
+ the pawn in front of blacks queen occupies square D7. Whites Knight
+ is on square B1 and can move to squares A3 and C3.
+
+ A8 B8 C8 D8 E8 F8 G8 H8 BR BN BB BQ BK BB BN BR
+ A7 B7 C7 D7 E7 F7 G7 H7 BP BP BP BP BP BP BP BP
+ A6 B6 C6 D6 E6 F6 G6 H6 -- ** -- ** -- ** -- **
+ A5 B5 C5 D5 E5 F5 G5 H5 ** -- ** -- ** -- ** --
+ A4 B4 C4 D4 E4 F4 G4 H4 -- ** -- ** -- ** -- **
+ A3 B3 C3 D3 E3 F3 G3 H3 ** -- ** -- ** -- ** --
+ A2 B2 C2 D2 E2 F2 G2 H2 WP WP WP WP WP WP WP WP
+ A1 B1 C1 D1 E1 F1 G1 H1 WR WN WB WQ WK WB WN WR
+
+ A move is specified by the square number of the piece that is moving,
+ an optional "-" or ":", and the square number that the piece is moving
+ to. Using this notation, the 2 possible moves for Whites Knight on
+ square B1 would be: B1-C3 and B1-A3. The symbol "O-O" is used to spec-
+ ify king side castling and the symbol "O-O-O" is used to specify queens
+ side castling. Pawn promotion moves are printed out in the same manner
+ as any other pawn move, except that they are followed by a "=" and
+ the initial of the piece the pawn is promoting to. For example, on
+ an empty board, a pawn on A7 would have 4 possible moves:
+
+ A7-A8=N A7-A8=B A7-A8=R A7-A8=Q
+
+ On input, if no equal sign and initial are specified, the promotion
+ is assumed to be to a queen.
+
+
+
+ (Note: CHEKMO-II uses the ':' symbol to indicate that a piece was taken
+ by that move. You may wish to type your moves in the same way.)
+
+\f
+
+ CHEKMO-II Chess Program for the PDP-8 Page 6
+
+
+ FORSYTHE NOTATION
+ -------- --------
+
+ Forsythe Notation uses the 2-letter codes shown on page 3 (and used
+ throughout this discussion) to specify the pieces and numbers to in-
+ dicate how many spaces occur between pieces. When entering a board
+ configuration each position in every row must be accounted for -
+ see the error message summary on page 4.
+
+ Example: BR4BK2 looks like: BR ** -- ** -- BK -- **
+
+
+ ERROR HALTS
+ ----- -----
+
+ There are 2 legitimate error halts possible with CHEKMO-II
+
+ Address Explanation
+
+ 5004 An unexplained interrupt has occurred. Press the CLEAR
+ and CONTINUE keys (START on a non-PDP-8/e). If the error
+ persists, try to find its cause and eliminate it. A likely
+ cause is a DF32 Disk Unit set to the OFF position.
+
+ 1761 The position has gotten too complex and CHEKMO-II's push
+ down list has overflowed. You Win!! Just before halting,
+ CHEKMO-II will print out. . .
+
+ I RESIGN
+
+
+ This error can probably only occur if one or both sides has
+ queened several pawns.
+
+ Halting at any other address is extremely unlikely, and is caused
+ either by a hardware failure, or an as yet unknown program bug.
+
+ KNOWN BUGS
+ ----- ----
+
+ There are no known "bugs" in CHEKMO-II Rev #62.
+
+ KNOWN DEFICIENCIES
+ ----- ------------
+
+ CHEKMO-II as of Rev. #62 does not recognize the value of passed pawns
+ until they reach the 6th or 7th rank.
+
+ CHEKMO-II has been programmed to use the same strategy throughout
+ the game. This strategy has been optimized for good play in the
+ Middlegame and Opening. As a result, CHEKMO-II plays poor moves
+ in some Endgame positions.
+\f
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