Emacs Chess: chess.el

Next:   [Contents][Index]

Emacs Chess: chess.el

Chess.el is an Emacs chess client and library, designed to be used for writing chess-related programs, or for playing games of chess against various chess engines, including Internet servers. The library can be used for analyzing variations, browsing historical games, or a multitude of other purposes.

The purpose of this manual is to help you understand how chess.el is structured for use as a library, and also how to use it as a client.

Table of Contents

1 The chess.el library

This chapter documents the low-level aspects of chess.el, mostly targeting developers interested in understanding the underlying APIs.

See Chessboard displays, and the chapters following it, if you are interested in the more user-visible aspects of chess.el.

1.1 Positions

A chess position is a given layout of pieces on a chess board, also reflecting which side (i.e., player) is next to move, and what privileges are currently available to each side (castling short or long, en passant capture, etc).

A position may be represented in ASCII using FEN (or EPD), or graphically by displaying a chess board. It is rather inconvenient to render them verbally.

The position can be represented on a remote terminal using X windows, or by transmitting the FEN string via a network connection or clipboard, to another chess board rendering tool. It may of course also be represented physically, by setting up the pieces to match the FEN specification.

Chess puzzles are most often provided as a set of positions.

1.1.1 Creating positions

Function: chess-pos-create &optional blank

Create a new chess position, set at the starting position. If blank is non-nil, all of the squares will be empty. The current side-to-move is always white.

Function: chess-pos-copy position

Copy the given chess position. If there are annotations or EPD opcodes set, these lists are copied as well, so that the two positions do not share the same lists.

Variable: chess-starting-position

Starting position of a chess game.

Function: chess-fischer-random-position

Generate a Fischer Random style position.

1.1.2 Position coordinates

First of all, position coordinates use a coordinate system of octal indices, where the index ‘?\044’ signifies rank 4 file 4 (i.e., "e4"). Rank is numbered 0 to 7, top to bottom, and file is 0 to 7, left to right.

Function: chess-index-rank index

Return the rank component of the given index.

Function: chess-index-file index

Return the file component of the given index.

Function: chess-rf-to-index rank file

Convert rank and file coordinates into an octal index.

For those who wish to use ASCII coordinates, such as "e4", there are two conversion functions:

Function: chess-coord-to-index coord

Convert a coord string into an index value.

Function: chess-index-to-coord index

Convert the chess position index into a coord string.

For fast manipulation of chess position indices, the following constants and functions are provided:

For queens and rooks:

Constant: chess-direction-north

Signify one step north, as seen from the perspective of the white player.

Constant: chess-direction-east

Signify one step east, as seen from the perspective of the white player.

Constant: chess-direction-south

Signify one step south, as seen from the perspective of the white player.

Constant: chess-direction-west

Signify one step west, as seen from the perspective of the white player.

For queens and bishops:

Constant: chess-direction-northeast

Signify one step northeast, as seen from the perspective of the white player.

Constant: chess-direction-southeast

Signify one step southeast, as seen from the perspective of the white player.

Constant: chess-direction-southwest

Signify one step southwest, as seen from the perspective of the white player.

Constant: chess-direction-northwest

Signify one step northwest, as seen from the perspective of the white player.

Function: chess-next-index index direction

Create a new index from an old one, by advancing it into direction. If the resulting index is not valid (outside the board), nil is returned.

Due to the underlying technique used to efficiently detect off-board squares, a direction specifier should at most do two steps in any direction. Directions can be combined, so that (* chess-direction-north 2) will give a typical initial white pawn push.

1.1.3 Position details

Given an octal index value, you can look up what’s on a particular square, or set that square’s value:

Function: chess-pos-piece position index

Return the piece on position at index.

Function: chess-pos-piece-p position index piece-or-color

Return non-nil if the given piece-or-color is at position/index. If piece-or-color is t for white or nil for black, any piece of that color will do.

Function: chess-pos-set-piece position index piece

Set the piece on position at index to piece. piece must be one of ?K, ?Q, ?N, ?B, ?R, or ?P for white pieces, or one of the corresponding lowercase letters for black pieces.

Function: chess-pos-search position piece-or-color

Look anywhere on position for piece-or-color, returning all coordinates. If piece-or-color is t for white or nil for black, any piece of that color will do.

Function: chess-pos-search* position &rest pieces

Look on position for any of pieces.

The result is an alist where each element looks like (piece . indices). Pieces which did not appear in position will be present in the resulting alist, but the cdr of their entries will be nil.

Function: chess-search-position position target piece &optional check-only no-castling

Look on position from target for a piece that can move there. This routine looks along valid paths of movement for piece. It differs from chess-pos-search, which is a more basic function that doesn’t take piece movement into account.

If piece is t or nil, valid piece movements for any piece of that color will be considered (t for white, nil for black). Otherwise, the letter-case of the piece determines color.

The return value is a list of candidates, which means a list of indices that indicate where a piece may have moved from.

If check-only is non-nil and piece is either t or nil, only consider pieces which can give check (not the opponent’s king). If no-castling is non-nil, do not consider castling moves.

Function: chess-pos-can-castle position side

Return whether the king on position can castle on side. The side argument must be either ‘?K’ for the king side, or ‘?Q’ for the queen side (use lowercase to query if black can castle).

Function: chess-pos-set-can-castle position side value

Set whether the king can castle on the given position on side.

See chess-pos-can-castle.

It is only necessary to call this function if setting up a position manually. Note that all newly created positions have full castling privileges set, unless the position is created blank, in which case castling privileges are unset. See chess-pos-create.

Function: chess-pos-en-passant position

Return the index of any pawn on position that can be captured en passant. Returns nil if en passant is unavailable.

Function: chess-pos-set-en-passant position index

Set the index of any pawn on position that can be captured en passant.

Function: chess-pos-status position

Return whether the side to move in the position is in a special state. Return nil if not, otherwise one of the keywords: :check, :checkmate or :stalemate.

Function: chess-pos-set-status position value

Set whether the side to move in position is in a special state. The value should either be nil, to indicate that the position is normal, or one of the symbols: check, checkmate, stalemate.

Function: chess-pos-side-to-move position

Return the color whose move it is in position.

Function: chess-pos-set-side-to-move position color

Set the color whose move it is in position.

Function: chess-pos-passed-pawns position color &optional pawn-indices

If color has Passed Pawns in position, return a list of their indices. Optionally, if indices is non-nil, those indices are considered as candidates.

A Pawn whose advance to the eighth rank is not blocked by an opposing Pawn in the same file and who does not have to pass one on an adjoining file is called a passed Pawn.

Variable: chess-pos-always-white

When set, it is assumed that white is always on move. This is really only useful when setting up training positions. This variable automatically becomes buffer-local when changed.

Function: chess-pos-move position &rest changes

Move a piece on the position directly, using the indices in changes. This function does not check any rules, it only makes sure you are not trying to move a blank square.

Next: , Previous: , Up: Positions   [Contents][Index]

1.1.4 Annotations

Function: chess-pos-annotations position

Return the list of annotations for this position.

Function: chess-pos-add-annotation position annotation

Add an annotation for this position.

Next: , Previous: , Up: Positions   [Contents][Index]

1.1.5 FEN notation

FEN (Forsyth-Edwards Notation) encodes a chess position using a simple string. The format is:

   position side castling en-passant

The position gives all eight ranks, by specifying a letter for each piece in the position, and a number for any intervening spaces; ranks are separated by slashes. Trailing spaces need not be counted. Uppercase letters signify white pieces, and lowercase black. For example, if your position only had a black king on d8, your position string would be:


for the three spaces (a, b and c file), the black king, and then all the remaining ranks (which are all empty, so their spaces can be ignored).

The side is ‘w’ or ‘b’, to indicate whose move it is.

The castling can contain ‘K’, ‘Q’, ‘k’ or ‘q’, to signify whether the white or black king can still castle on the king or queen side. If neither color can castle on any side, ‘-’ should be provided.

The en-passant signifies the target square of an en passant capture, such as ‘e3’ or ‘a6’.

Function: chess-fen-to-pos fen

Convert the FEN string fen to a chess position.

Function: chess-pos-to-fen position &optional full

Convert a chess position to a FEN string. If full is non-nil, represent trailing spaces as well.

This is how the starting position looks like:

 (chess-pos-to-fen chess-starting-position)
 ⇒ "rnbqkbnr/pppppppp/////PPPPPPPP/RNBQKBNR w KQkq -"

Some external programs might have problems parsing terse FEN strings. If you are unsure, use the more verbose form:

 (chess-pos-to-fen chess-starting-position t)
 ⇒ "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq -"

Previous: , Up: Positions   [Contents][Index]

1.1.6 EPD notation

EPD (Extended Position Description) is a standard for describing chess positions along with an extended set of structured attribute values using the ASCII character set. It is intended for data and command interchange among chess-playing programs. It is also intended for the representation of portable opening library repositories.

A single EPD uses one text line of variable length composed of four data fields, followed by zero or more operations. The four fields of the EPD specification are the same as the first four fields of the FEN specification (see FEN notation).

A text file composed exclusively of EPD data records should have a file name with the .epd extension.

Function: chess-epd-to-pos &optional string

Convert extended position description string to a chess position. If string is not specified, look for an EPD string in the current buffer, and advance point after the correctly parsed position.

Function: chess-pos-to-epd position

Convert a chess position to a string representation in extended position description format.

Function: chess-epd-read-file file

Return a list of positions contained in file. Operations

An EPD operation is composed of an opcode followed by zero or more operands, and terminated by a semicolon.

Multiple operations are separated by a single space character. If there is at least one operation present in an EPD record, it is separated from the last (fourth) data field by a single space character.

Some opcodes that allow for more than one operand may have special ordering requirements for the operands. For example, the ‘pv’ (predicted variation) opcode requires its operands (moves) to appear in the order in which they would be played. All other opcodes that allow for more than one operand should have operands appearing in ASCII order. An example of the latter set is the ‘bm’ (best move[s]) opcode; its operands are moves that are all immediately playable from the current position. Opcode ‘acd’ analysis count depth

The opcode ‘acd’ takes a single non-negative integer operand. It is used to represent the depth of the ply (see Plies) examined in an analysis. Opcode ‘acn’ analysis count nodes

The opcode ‘acn’ takes a single non-negative integer operand. It is used to represent the number of nodes examined in an analysis. Note that the value may be quite large for some extended searches, and so use of (at least) a long (four byte) representation is suggested. Opcode ‘acs’ analysis count seconds

The opcode ‘acs’ takes a single non-negative integer operand. It is used to represent the number of seconds used for an analysis. Note that the value may be quite large for some extended searches, and so use of (at least) a long (four byte) representation is suggested. Opcode ‘am’ avoid move(s)

The opcode ‘am’ indicates a set of zero or more moves, all immediately playable from the current position, that are to be avoided in the opinion of the EPD writer. Each operand is a SAN move; they appear in ASCII order. Opcode ‘bm’ best move(s)

The opcode ‘bm’ indicates a set of zero or more moves, all immediately playable from the current position, that are judged to the best available by the EPD writer. Each operand is a SAN move; they appear in ASCII order.

1.2 Plies

A ply is the differential between two positions. In other words, it is the coordinate transformations applied to one position in order to arrive at the following position. It is also informally called "a move".

A ply may be represented in ASCII by printing the FEN string of the base position, and then printing the positional transformation in algebraic notation. Since the starting position is usually known, the FEN string is optional. A ply may be represented graphically by moving the chess piece(s) involved. It may be rendered verbally by voicing which piece is to move, where it will move to, and what will happen a result of the move (piece capture, check, etc).

Plies may be sent over network connections, postal mail, e-mail, etc., so long as the current position is maintained at both sides. Transmitting the base position’s FEN string along with the ply offers a form of confirmation during the course of a game.

Next: , Up: Plies   [Contents][Index]

1.2.1 Creating plies

Function: chess-ply-create position &optional valid-p &rest changes

Create a ply from the given position by applying the supplied changes. This function will guarantee the resulting ply is valid, and will also annotate the ply with :check or other modifiers as necessary. It will also extend castling, and will prompt for a promotion piece.

Note: Do not pass in the rook move if changes represents a castling maneuver.

Function: chess-legal-plies position &rest keywords

Return a list of all valid plies in position. The allowed keywords are:


Return t if any piece can move at all.

:color boolean

If boolean is t, return plies for white, if nil, return plies for black.

:piece character

Return plies for a specific piece designated by character.

:file file

Given a file, a number (0-7), return plies for any piece or color present on that file. :piece or :color must be present.

:index index

Return plies for the piece at index.

:target index

Return plies that go to a specific coordinate specified by index.

:candidates index...

If provided, only consider the source coordinates specified by the indices.

These will constrain the plies generated to those matching the above criteria.

NOTE: All of the returned plies will reference the same copy of the position object passed in.

1.2.2 Ply details

Function: chess-ply-pos ply

Return the base position associated with ply.

Function: chess-ply-set-pos ply position

Set the base position of ply.

Function: chess-ply-changes

Return the coordinate transformations and keywords associated with this ply.

Value is a list made of a pair of indices (or two pairs, in case of castling) followed by optional keywords.

Function: chess-ply-set-changes

Set the coordinate transformations and keywords associated with this ply.

Function: chess-ply-source ply

Return the source square index value of ply.

Function: chess-ply-target ply

Return the target square index value of ply.

For example, here is how to find the source square of a freshly created ply:

 (chess-ply-source (chess-ply-create chess-starting-position nil
                                     (chess-coord-to-index "e2")
                                     (chess-coord-to-index "e4")))
 ⇒ 52

Next: , Previous: , Up: Plies   [Contents][Index]

1.2.3 The “next” position

Function: chess-ply-next-pos ply

Return the position that results from executing ply.

Function: chess-ply-final-p ply

Return non-nil if this is the last ply of a game/variation.

1.2.4 Algebraic notation

A thing to deal with in chess is algebraic move notation, such as ‘Nxf3+’. This notation is a shorthand way of representing where a piece is moving from and to, by specifying the piece involved, where it’s going, and whether or not a capture or check is involved.

You can convert from algebraic notation to a ply using the following function:

Function: chess-algebraic-to-ply position move &optional trust

Convert the algebraic notation move for position to a ply.

If optional argument trust is non-nil, accept check or checkmate symbols (‘+’ and ‘#’) as given.

The function also checks if a move is valid, and will raise an error if not.

To convert from a ply to algebraic notation, use:

Function: chess-ply-to-algebraic ply &optional type

Convert the given ply to algebraic notation (a string).

Optional argument type specifies the kind of algebraic notation to generate:


Generate short (or standard) algebraic notation. This is the default.


Generate long algebraic notation (like ‘Nb1-c3’).


Generate figurine algebraic notation (uppercase letters will be replaced by Unicode chess figures).


Generate ICCF numeric notation as used in correspondence chess (like ‘2133’).

Lastly, there is a regexp for quickly checking if a string is in algebraic notation or not, or searching out algebraic strings in a buffer:

Variable: chess-algebraic-regexp

A regular expression that matches all possible algebraic moves. This regexp handles short, long and figurine algebraic notation.

Next: , Previous: , Up: The chess.el library   [Contents][Index]

1.3 Variations

A variation is a sequence of plies that occur after some starting position. If the starting position represents the initial setup of a chess board, and if the final ply results in completion of the game, it is called “the main variation”. Otherwise, variations typically represented interesting tangents during a game—but not actually played—as envisioned by the player, an annotator, or someone studying the game.

Variations may be represented in ASCII by stating the FEN string for starting position, followed by the list of plies that follow that position. They are difficult to represent graphically, except for showing each position in turn with a slight pause between—or by allowing the user to navigate each of the subsequent positions in turn. They may be represented verbally by announcing each of the plies in turn, as mentioned above.

1.3.1 Creating variations

Function: chess-var-create &optional position

Create a new chess variation object. Optionally, use the given starting position.

1.3.2 Variation positions

Function: chess-var-pos variation &optional index

Return the position related to variation’s index ply.

Function: chess-var-index variation

Return the variation’s current position index.

Function: chess-var-seq variation

Return the current variation sequence.

Function: chess-var-side-to-move variation &optional index

Return the color whose move it is in variation at index (or at the last position of variation if index is nil).

1.3.3 Variation plies

Function: chess-var-ply variation &optional index

Return variation’s indexth ply.

Function: chess-var-plies variation

Return the plies of variation.

Function: chess-var-to-algebraic variation &optional long

Reveal the plies of variation by converting them to algebraic notation.

Previous: , Up: Variations   [Contents][Index]

1.3.4 Making a move in a variation

Function: chess-var-move variation ply

Make a move in the current variation by applying the changes of ply. This creates a new position and adds it to the main variation. The ‘changes’ of the last ply reflect whether the var is currently in progress (nil), if it is drawn, resigned, mate, etc.

Function: chess-var-add-ply variation ply

Add the given ply to variation.

1.4 Games

A game includes its main variation, incidental information about the game (who played it, where, when, who won, etc.), and any sub-variations of interest to those studying the game afterwards.

Game tags is an alist that associates arbitrary English tag names to their values.

A game may be represented in ASCII using PGN (Portable Game Notation). Representing them graphically or verbally is similar to what is done for variations (see Variations).

Function: chess-game-add-hook game function &optional data prepend

Add to game an event hook function.

Function: chess-game-add-ply game ply

Add ply to the main variation of game.

Function: chess-game-hooks game

Return the event hooks associated with game.

Function: chess-game-plies game

Return the main variation of game as a list of plies.

Function: chess-game-remove-hook game function &optional data

Remove from game all event hooks that match function. If data is specified, only remove hooks with matching associated data.

Function: chess-game-run-hooks game &rest args

Run the event hooks of game and pass it args.

Function: chess-game-set-hooks game hooks

Set the event hooks associated with game.

Function: chess-game-set-plies game plies

Set the list of plies which represents the main variation of game.

Next: , Up: Games   [Contents][Index]

1.4.1 Creating games

Function: chess-game-create &optional position tags

Create a new chess game object. Optionally use the given starting position. tags is the starting set of game tags (which can always be changed later using the various tag-related methods).

Next: , Previous: , Up: Games   [Contents][Index]

1.4.2 Game tags

Function: chess-game-tags game

Return the tags alist associated with game.

Function: chess-game-set-tags game tags

Set the tags alist associated with game. After the tags alist was set the ‘set-tags’ event is triggered.

Function: chess-game-tag game tag

Return the value for tag in game.

Function: chess-game-set-tag game tag value

Set the tag for game to value.

Function: chess-game-del-tag game tag

Delete the specified tag from game.

Next: , Previous: , Up: Games   [Contents][Index]

1.4.3 Game positions

Function: chess-game-pos game &optional index

Return the current position of game or a position of a given index.

Function: chess-game-index game

Return the game’s current position index.

Function: chess-game-seq game

Return the current game sequence number.

Function: chess-game-side-to-move game &optional index

Return the side, specified as color, whose move it is in game at index (or at the last position if index is nil). Value is t for white and nil for black.

Next: , Previous: , Up: Games   [Contents][Index]

1.4.4 Game plies

Function: chess-game-ply game &optional index

Return a ply of game. If index is non-nil, the last played ply is returned.

Next: , Previous: , Up: Games   [Contents][Index]

1.4.5 Making a move

Function: chess-game-move game ply

Make a move in the current game using ply. This creates a new position and adds it to the main variation. The ‘changes’ of the last ply reflect whether the game is currently in progress (nil), if it is drawn, resigned, mate, etc.

Previous: , Up: Games   [Contents][Index]

1.4.6 PGN notation

Function: chess-pgn-to-game &optional string

Convert the PGN notation at point into a chess game. Optionally use the supplied string instead of the current buffer.

Function: chess-game-to-pgn game &optional indented to-string

Convert a chess game to PGN notation. If indented is non-nil, indent the move texts. If to-string is non-nil, return a string instead of inserting the resulting PGN text.

Function: chess-pgn-insert-plies game index plies &optional for-black indented no-annotations

NYI: Still have to implement the indented argument. PGN mode

Function: chess-pgn-visualize

Visualize the move for the PGN game under point. This does not require that the buffer be in PGN mode.

1.5 Collections

A collection is a set of games archived for later perusal. A set of games conceptually represents a large tree of branching variations, and can be used for studying current theory, examining Master preferences, etc.

Chess.el itself does not attempt to provide library services, nor does it ever represent library collections in memory. Instead, it interacts with a chess database engine for the purpose of storing and retrieving games from the library, or performing library-wide analyses and searches.

1.5.1 Opening Databases

Variable: chess-database-modules

List of database modules to try when chess-database-open is called.

Function: chess-database-open file &optional module

Open a game database specified by file. You can optionally specify the database module to use.

Returns the opened database object, or nil.

1.5.2 Querying Databases

Function: chess-database-filename database

Return the filename of an already opened database.

Function: chess-database-read database index

Return from database the chess game object at index.

Function: chess-database-query database &rest terms

Run a query on database. The terms are partly dependent on the chess-database module in use. For the ‘chess-scid’ module, using tree-search game means perform a tree search on the last position of game.

1.5.3 Modifying Databases

Function: chess-database-read-only-p database

Return non-nil if database is read only.

1.5.4 Finalizing Databases

1.5.5 Database Modules

Currently, there are two subclasses of the above defined database base-class: chess-file

This module does not use an external chess database program to store and retrieve games. It uses the PGN of EPD format parsing routines provided in chess-pgn.el and chess-epd.el to implement collections for ordinary PGN and EPD files.

EPD file collections are represented as a collection of games originating at the given position. One might argue that conceptually, they represent a collection of positions, but it is more convenient to merge all collections into one uniform concept.

Previous: , Up: Database Modules   [Contents][Index] chess-scid

This module implements basic reading and writing functionality for SCID (Shane’s Chess Information Database) files.

1.6 Chess Opening Books

There are two different modules/libraries provided for looking up chess positions in opening books.

1.6.1 ECO Classification

Module chess-eco provides a database of well known names for chess opening positions. If this module is activated (see variable chess-default-modules), known chess opening positions will be announced in the minibuffer during a game.

1.6.2 Polyglot opening book format support

The popular and freely documented Polyglot opening book format is supported. There is a default polyglot book file shipped with chess.el to support engines which do not have built-in support for looking up positions in opening books (such as some UCI protocol based engines).

User Option: chess-polyglot-book-file

Path to default polyglot book file.

Variable: chess-polyglot-book

If non-nil, the buffer holding the currently loaded polyglot book data.

This is used by UCI based engine modules as well as the internal AI.

Function: chess-polyglot-book-open file

Open a polyglot book file.

Returns a buffer object which contains the binary data.

Function: chess-polyglot-book-plies book position

Return a list of plies found in book for position. The resulting list is ordered, most interesting plies come first. The :polyglot-book-weight ply keyword is used to store the actual move weights. Use chess-ply-keyword on elements of the returned list to retrieve them.

Function: chess-polyglot-book-ply book position &optional strength

If non-nil, a (randomly picked) ply from book for position. Random distribution is defined by the relative weights of the found plies. If non-nil, strength defines the bias towards better moves. A value below 1.0 will penalize known good moves while a value above 1.0 will prefer known good moves. The default is the value of chess-polyglot-book-strength. A strength value of 0.0 will completely ignore move weights, and evenly distribute the probability that a move gets picked.

2 Modules

Positions, plies and variations are typically accessed in reference to a game object, which has a main variation containing the plies and positions that represent the number of moves made within that game up to the final position.

Another thing that the game object does is to manage events that occur within that game. If a move is made from the final position, for example, it will cause a new ply to be created, adding it to the end of the main variation. Then, a ‘move’ event is triggered within the game and passed to any chess modules which are currently associated with that game. The concept of modules allows far more complex aspects of chess playing to be dealt with, while allowing the library itself to still operate solely in terms of the game object.

For example, although the plies of a game object contain all the information the computer needs to follow the game, a user needs much more. He wants to see the pieces move. To support this, a display module (see Chessboard displays) can be created, and linked to the game. The first effect of this association will be to create a chess board display and show the game’s final position on it. Now whenever plies are added to the game, the chess board will be updated to show the effect of that move on the board. The display module realizes that a move has been made by receiving the ‘move’ event which is passed to all modules associated with the game object.

There may be any number of modules associated with a chess game, and they may do anything you like. Basically, for a module called ‘chess-sample’, a function must exist called chess-sample-handler. This takes two or more arguments: a game object, the event symbol, and whatever other arguments were passed along with the event symbol.

When an event is triggered on a game object (this may happen as a byproduct of manipulating the game, or events may be manually generated), every associated module, in order, is called with that event and whatever arguments were passed along with the event. The game object is passed also, so that the module knows which game this event has occurred in reference to.

Once called, the module can do whatever it likes. Some events expect certain values to be returned, to indicate success or failure in processing the event. There are many different events, each depicting something specific that might happen in the context of playing or manipulating a chess game. Some events relate only to the chess game itself, some are triggered by the various chess engines that might be associated with that game. Modules may even trigger events in response to event. The game itself remains unaware of events, except for the fact that it will pass them along to every module associated with that game.

This is how displays get updated, for example, because once a ‘move’ event is triggered, each display knows that it must now look at the new final position and update its display. It may even trigger new events special to displays, to cause a refresh to happen after update calculations have been performed, for example. All such details are left to the module, and the game does not interfere with such intra-module messaging.

Looked at as an object-oriented design, these are typical polymorphic events. Certain generic situations frequently occur, such as moves, which trigger events so that everyone concerned with the game can be updated as to the move that occurred. This way, no one need to actively query the game to find out if something new has happened. The game will notify every listening module by sending an event.

The core library, which consists of code to manipulate games, does not define any modules. The rest of the chess.el library is strictly a set of module implementations, of various types. Display modules react to moves, and may modify the game based on user input; engine modules react to moves by notifying the engine of the move; network client modules react to moves by sending the move text over the network. Engine and network modules may also trigger new events when the engine or network player has decided on their move, and this move is then applied to the game object.

At the moment, no negotiation is done to determine which module may modify the game object. All modules have equal privilege. This means it is the programmer’s duty not to associate conflicting modules with a single game object. If two artificial intelligence engines were linked, for example, they would quickly start stepping on each other’s toes. But it is perfectly fine to have one artificial intelligence engine, and another passive engine whose only purpose is to relay the moves to a networked observer on another computer. The possibilities are endless.

Modules are very easy to write, although engines and displays are rather different from each other in their principles. There is a base engine, and a base display, which receive the same events as any other module. But then there are derived engines and derived displays which trigger a whole family of events specific to those module types. If you suspect a bug in your module, put a breakpoint in your handler function, and wait for the offending event to come through. Then you can watch what your module does in response to that event. If it leaves the game object alone, it should be easy to locate the problem, since it will always be within the module itself. But if your module also modifies the game object in response to certain events, you may induce a feedback loop that is much more difficult to sort out. Test often and keep in mind that many events might end up coming through as a result of the game changes your module makes!

That, in essence, is how the module system works. From the game object’s perspective, it is a very simple mechanism, much like a function ring or a hook. The hook is called at certain points, so that any listener can react to changes in the game. But from each module’s perspective, it is a rich way to allow inter-operation between both passive and reactive modules, all of them acting together to enrich the context of play involving the central game object.

The only other rule to be mentioned is that each module instance should be associated with only one game object at a time, although a game object may have unlimited modules of any type linked to it. Otherwise, trying to update a chess board based on input from two different games would get impossible to sort out. Better to create a new board for every game—the way ordinary humans would do it in the real world.

Next: , Previous: , Up: Emacs Chess: chess.el   [Contents][Index]

3 Chessboard displays

The previous chapter described all the objects found in chess—positions, plies, variations, games and collections. However, these objects can only be manipulated programmatically using the functions given so far. In order to present them in a meaningful fashion to a human reader, it is necessary to create and use a display object.

3.1 Generic display manipulation functions

Function: chess-display-create game style perspective

Create a chess display, for displaying chess objects. The game is the chess game object to use, style should be the display type to use (a symbol), and perspective determines the viewpoint of the board: if non-nil, the board is viewed from White’s perspective.

Function: chess-display-active-p

Return non-nil if the displayed chessboard reflects an active game. Basically, it means we are playing, not editing or reviewing.

Function: chess-display-clear-board

Setup the current board for editing.

Function: chess-display-highlight display &rest args

Highlight in display the squares given in args on the current position.

The args is a list of highlighting modes and position coordinates. The default highlighting mode is :selected which is supported by most displays.

Function: chess-display-invert

Invert the perspective of the current chess board.

Function: chess-display-move display ply

Move a piece on display, by applying the given ply. The position of ply must match the currently displayed position.

Function: chess-display-perspective display

Return the current perspective of display.

Function: chess-display-position display

Return the position currently viewed on display.

Function: chess-display-quit

Quit the game associated with the current display.

Function: chess-display-set-game display game &optional index

Set the given display to display the game object, optionally at index. This is the function to call to cause a display to view a game. It will also update all of the listening engines and other displays to also view the same game.

Function: chess-display-set-perspective display perspective

Set perspective of display.

Function: chess-display-set-position display &optional position my-color

Set the game associated with display to use position and my-color.

Function: chess-display-set-variation display variation &optional index

Set display variation. If index is not specified, this will cause the first ply in the variation to be displayed, with the user able to scroll back and forth through the moves in the variation. Any moves made on the board will extend/change the variation that was passed in.

Function: chess-display-update display &optional popup

Update the chessboard display. If popup is non-nil, make sure it is visible.

3.2 Chess display mode

Chess display mode is a special major mode (see (emacs)Major Modes) that allows to select pieces to move with the mouse or by moving point to the desired square/piece. Additionally, you can enter moves in a variant of algebraic notation via the keyboard.

All the chessboard displays described in following sub-sections share the basic behavior provided by chess display mode. They basically only differ in appearance of the various chessboards.

User Option: chess-display-highlight-legal

If non-nil, highlight valid target squares when a piece is selected.

3.2.1 Basic operations


Invert the perspective of the current chess board (chess-display-invert).


Show the previous move in the current game (chess-display-move-backward).


Find previous move which algebraic notation matches a regular expression (chess-display-search-backward).


Find next move which algebraic notation matches a regular expression (chess-display-search-forward).


Show the next move in the current game (chess-display-move-forward).


Move to the initial position of the current game (chess-display-move-first).


Move to the last position of the current game (chess-display-move-last).

C-c C-d

Offer to draw the current game (chess-display-draw).

C-c C-r

Resign the current game (chess-display-resign).

C-u M-w

Copy the currently displayed position to the kill ring as a FEN string (chess-display-kill-board).

With prefix argument, copy the current game in PGN to the kill ring.


Set the current display position via a FEN string from the kill ring (chess-display-yank-board).

This is useful to copy positions from one chessboard display to another, as well as quickly setting up a position from a FEN string previously added to the kill ring from somewhere else.


Quit this chessboard display (chess-display-quit).

This destroys the session (and all related modules) associated with this chessboard display.

3.2.2 Selecting pieces with the keyboard

In character based chessboard displays, point can be moved around in the buffer as usual. You can indicate the initial square/piece and the target square/piece by moving point to the desired position and pressing RET.


Select the piece/square currently indicated by point (chess-display-select-piece) to move from/to.

3.2.3 Selecting pieces with the mouse

Similarly, you can also use the mouse (if available) to indicate the source and target square of your move.


Select the piece/square currently indicated by the mouse pointer (chess-display-select-piece) to move from/to.

3.2.4 Entering moves with algebraic notation


Enter move in algebraic notation.

The move will be accepted as soon as it is unambiguous. So in most situations, you do not need to type the complete algebraic move string. For instance, if there is only one piece which can be taken by one of your knights, typing N x is sufficient to select that move.

Additionally, the characters x and = are optional, as there is no difference between N x e 4 and N e 4.


Delete the last entered chess move character (chess-input-shortcut-delete).

This is useful if you have accidentally typed a wrong character, and the move was not unambiguous yet.

3.3 Plain ASCII diagram displays

The simplest display style available is chess-plain, a very customizable ASCII board diagram display.

This is how the starting position looks in its default configuration:

8|r n b q k b n r|
7|p p p p p p p p|
6|. . . . . . . .|
5|. . . . . . . .|
4|. . . . . . . .|
3|. . . . . . . .|
2|P P P P P P P P|
1|R N B Q K B N R|
  a b c d e f g h
User Option: chess-plain-separate-frame

If non-nil, display the chessboard in its own frame.

User Option: chess-plain-border-style

If non-nil, a vector of Characters used to draw borders.

Otherwise, omit to draw any border around the chessboard diagram.

User Option: chess-plain-black-square-char

Character used to indicate empty black squares.

User Option: chess-plain-white-square-char

Character used to indicate black white squares.

User Option: chess-plain-piece-chars

Alist of pieces and their corresponding characters.

User Option: chess-plain-upcase-indicates

Defines what an upcase char should indicate. The default is 'color, meaning a upcase char is a white piece, a lowercase char a black piece. Possible values: 'color (default), 'square-color. If set to 'square-color, an uppercase character indicates a piece on a black square. (Note that you also need to modify chess-plain-piece-chars to avoid real confusion.)

User Option: chess-plain-spacing

Number of spaces between files.

To customize options of chess-plain, use M-x customize-group RET chess-plain RET.

3.4 ICS1 style ASCII displays

The chess-ics1 module is a more verbose ASCII chessboard display.

This is how the starting position looks with this chessboard display:

    8 | r | n | b | q | k | b | n | r |
    7 | p | p | p | p | p | p | p | p |
    6 |   |   |   |   |   |   |   |   |
    5 |   |   |   |   |   |   |   |   |
    4 |   |   |   |   |   |   |   |   |
    3 |   |   |   |   |   |   |   |   |
    2 | P | P | P | P | P | P | P | P |
    1 | R | N | B | Q | K | B | N | R |
        a   b   c   d   e   f   g   h
User Option: chess-ics1-separate-frame

If non-nil, display the chessboard in its own frame.

To customize options of chess-ics1, use M-x customize-group RET chess-ics1 RET.

3.5 Graphical displays

The graphical chessboard display (chess-images) uses image files to create a visually appealing chessboard in a buffer.

User Option: chess-images-directory

A directory which contains images in XPM format.

If you want to draw your own images, each image file must be named color-piece.xpm, where color is either black or white, and piece is one of rook, knight, bishop, queen, king or pawn.

The only image format currently supported is XPM.

User Option: chess-images-separate-frame

If non-nil, display the chessboard in its own frame.

For all customization options of chess-images, use M-x customize-group RET chess-images RET.

4 Engines

Engines represent opponents in Chess. The main type of engine interfaces with an external chess program. However, there can be other uses for engine objects, such as providing networked engined for playing with opponent over different types of transports.

4.1 Common functions

Function: chess-engine-create module game &optional response-handler &rest handler-ctor-args

Create a new chess engine module (a symbol) associated with game. Optionally supply a new response-handler.

Function: chess-engine-set-option engine option value

Set engine option to value by invoking its handler with the ‘set-option’ event.

Function: chess-engine-position engine

Return the current position of the game associated with engine.

Function: chess-engine-command engine event &rest args

Call the handler of engine with event (a symbol) and args.

Function: chess-engine-send engine string

Send the given string to engine. If chess-engine-process is a valid process object, use process-send-string to submit the data. Otherwise, the ‘send’ event is triggered and the engine event handler can take care of the data.

Next: , Previous: , Up: Engines   [Contents][Index]

4.2 The Null Engine

The most basic engine module is chess-none, a stub module that does nothing. This is useful for a game of chess against another human, where both use the same computer to enter moves and display the current chess position.

It can also be useful for creating FEN strings of specific positions.

To bring up a chessboard with no active engine attached, use C-u M-x chess RET none RET.

Next: , Previous: , Up: Engines   [Contents][Index]

4.3 AI

The AI engine module defines a pure Emacs Lisp implementation of an opponent. Contrary to all other engine modules mentioned later on, it does not require any external programs to be installed.

To explicitly select this engine as an opponent, use C-u M-x chess RET ai RET.

User Option: chess-ai-depth

Defines the default search depth for this engine.

User Option: chess-ai-quiescence-depth

Defines the number of plies to search for a quiet position. This is in addition to chess-ai-depth.

If you’d like to employ the search and evaluation functions provided by this module programmatically, the following function is the top-level entry point.

Function: chess-ai-best-move position &optional depth eval-fn

Find the supposedly best move (ply) for position. depth defaults to the value of chess-ai-depth.

Next: , Previous: , Up: Engines   [Contents][Index]

4.4 Crafty

Crafty is a chess program written by Michael Byrne, UAB professor Dr. Robert Hyatt, Tracy Riegle, Peter Skinner and Ted Langreck. It is directly derived from Cray Blitz, winner of the 1983 and 1986 World Computer Chess Championships.

If the crafty program is installed and can be found in the program search path (exec-path), the chess-crafty engine module will automatically detect it.

If crafty is installed in a non-standard location, variable chess-crafty-path can be set to point to its executable file.

If you have multiple engines installed you can explicitly select to play against Crafty by invoking C-u M-x chess RET crafty RET.

Next: , Previous: , Up: Engines   [Contents][Index]

4.5 Fruit

Fruit is a chess engine developed by Fabien Letouzey. It was commercially available from September 2005 until July 2007. Now it is freeware and you can download it for free from http://www.fruitchess.com/. The development on Fruit by Fabien Letouzey has ceded and it is unlikely to continue.

Fruit was vice world computer chess champion 2005.

If the fruit command is installed and can be found in the program search path (exec-path), the chess-fruit engine module will automatically detect it.

If Fruit is installed in a non-standard location, variable chess-fruit-path can be set to point to its executable file.

If you have multiple engines installed you can explicitly select to play against Fruit by invoking C-u M-x chess RET fruit RET.

Next: , Previous: , Up: Engines   [Contents][Index]

4.6 Glaurung

Glaurung is another freely distributed strong computer chess engine.

If the glaurung program is installed and can be found in the program search path (exec-path), the chess-glaurung engine module will automatically detect it.

If Glaurung is installed in a non-standard location, variable chess-glaurung-path can be set to point to its executable file.

If you have multiple engines installed you can explicitly select to play against Glaurung by invoking C-u M-x chess RET glaurung RET.

Next: , Previous: , Up: Engines   [Contents][Index]

4.7 GNU Chess

GNU Chess is free software, licensed under the terms of the GNU General Public License, and is maintained by collaborating developers. As one of the earliest computer chess programs with full source code available, it’s one of the oldest for Unix-based systems and has since been ported to many other platforms.

If the gnuchess program is installed and can be found in the program search path (exec-path), the chess-gnuchess engine module will automatically detect it.

If GNU Chess is installed in a non-standard location, variable chess-gnuchess-path can be set to point to its executable file.

If you have multiple engines installed you can explicitly select to play against GNU Chess by invoking C-u M-x chess RET gnuchess RET.

Next: , Previous: , Up: Engines   [Contents][Index]

4.8 Phalanx

Phalanx is an old, popular chess engine, with an interesting history.

If the phalanx program is installed and can be found in the program search path (exec-path), the chess-phalanx engine module will automatically detect it.

If Phalanx is installed in a non-standard location, variable chess-phalanx-path can be set to point to its executable file.

If you have multiple engines installed you can explicitly select to play against Phalanx by invoking C-u M-x chess RET phalanx RET.

Next: , Previous: , Up: Engines   [Contents][Index]

4.9 Sjeng

Sjeng is a championship-winner automated chess engine developed by Gian-Carlo Pascutto from Belgium. While its original version was free, recent developments are for sale.

If the sjeng program is installed and can be found in the program search path (exec-path), the chess-sjeng engine module will automatically detect it.

If Sjeng is installed in a non-standard location, variable chess-sjeng-path can be set to point to its executable file.

If you have multiple engines installed you can explicitly select to play against Sjeng by invoking C-u M-x chess RET sjeng RET.

Previous: , Up: Engines   [Contents][Index]

4.10 Stockfish

Stockfish is one of the strongest chess engines in the world, appearing near or at the top of most chess engine rating lists. Stockfish is also free software, licensed under the terms of the GNU General Public License.

If the stockfish program is installed and can be found in the program search path (exec-path), the chess-stockfish engine module will automatically detect it.

If Stockfish is installed in a non-standard location, variable chess-stockfish-path can be set to point to its executable file.

If you have multiple engines installed you can explicitly select to play against Stockfish by invoking C-u M-x chess RET stockfish RET.

5 Chess Session

A chess session assembles all modules mentioned in previous chapters into a working system to interact with. A session typically consists of at least one display module, one engine module, and possibly a number of optional modules. All these modules share a common game object which is used to keep track of the currently active game.

Function: chess engine disable-popup engine-response-handler &rest engine-ctor-args

Play a game against engine.

This function constructs all the necessary modules required for a chess session. In particular, it will start engine and create a chess display as configured in chess-default-display.

This is the main entry-point for interactively launching a chessboard display with associated engine.

If you want to launch a chess session as part of your own code, the probably more expressive alias chess-session might be interesting to use.

You can have several active chess sessions. In fact, some features later described in this manual make use of this, see Internet Chess Servers.

To interactively start a chess session, invoke M-x chess RET. This uses chess-default-display to determine the chessboard display to use, and chess-default-engine to determine an opponent.

If you want to play against a specific engine, provide a prefix argument as in C-u M-x chess RET, which will prompt for an engine module. The module name has the common prefix ‘chess-’ stripped. So you enter gnuchess to indicate you’d like to play against the chess-gnuchess module.

6 Internet Chess Servers

Based on the services provided above, there is also a special mode for communication with Internet Chess Servers.

On an Internet Chess Server you can seek to play against other human or computer players, observe other games being played or examined, play tournaments, chat with fellow chess players, participate in team games, or do various other interesting chess related things.

A default set of well known servers is defined in the following variable:

Variable: chess-ics-server-list

A list of servers to connect to. The format of each entry is:

(server port [handle] [password-or-filename] [helper] [helper args...])

Internet Chess Servers based on FICS (Free Internet Chess Server) and ICC (Internet Chess Club) are currently supported.

6.1 Connecting to a server

To open a new connection to an Internet Chess Server, use:

Function: chess-ics server port &optional handle password-or-filename helper &rest helper-args

Connect to an Internet Chess Server.

If called interactively, you will be prompted to enter a server (from chess-ics-server-list and possibly identification credentials.

6.2 Chess ICS Mode

The major mode for ICS buffers is Chess ICS mode. Many of its special commands are bound to the C-c prefix. Here is a list of ICS mode commands:


Send the current line as input to the server (comint-send-input). Any prompt at the beginning of the line is omitted. If point is at the end of buffer, this is like submitting the command line in an ordinary interactive shell. However, you can also invoke RET elsewhere in the ICS buffer to submit the current line as input.


Either delete a character or send EOF (End Of File) (comint-delchar-or-maybe-eof). Typed at the end of the ICS buffer, this sends EOF to the server and terminates the connection. Typed at any other position in the buffer, this deletes the character at point, as usual.

C-c C-a

Move to the beginning of the line, but after the prompt if any (comint-bol-or-process-mark). If you repeat this command twice in a row, the second time it moves back to the process mark, which is the beginning of the input that you have not yet sent to the server. (Normally that is the same place—the end of the prompt on this line—but after C-c SPC the process mark may be in a previous line.)


Accumulate multiple lines of input, then send them together (comint-accumulate). This command inserts a newline before point, but does not send the preceding text as input to the server—at least, not yet. Both lines, the one before this newline and the one after, will be sent together (along with the newline that separates them), when you type RET.

C-c C-u

Kill all text pending at end of buffer to be sent as input (comint-kill-input). If point is not at end of buffer, this only kills the part of this text that precedes point.

C-c C-w

Kill a word before point (backward-kill-word).

C-c C-o

Delete the last batch of output from an ICS server command (comint-delete-output). This is useful if a server command spews out lots of output that just gets in the way.

C-c C-s

Write the last batch of output from an ICS server command to a file (comint-write-output). With a prefix argument, the file is appended to instead. Any prompt at the end of the output is not written.

C-c C-r

Scroll to display the beginning of the last batch of output at the top of the window; also move the cursor there (comint-show-output).

C-c C-e

Scroll to put the end of the buffer at the bottom of the window (comint-show-maximum-output).

M-x comint-truncate-buffer

This command truncates the ICS buffer to a certain maximum number of lines, specified by the variable comint-buffer-maximum-size. Here’s how to do this automatically each time you get output from the server:

(add-hook 'comint-output-filter-functions

ICS mode is a derivative of Comint mode, a general-purpose mode for communicating with interactive subprocesses. Most of the features of ICS mode actually come from Comint mode, as you can see from the command names listed above.

6.3 ICS Command History

ICS buffers support two ways of repeating earlier commands. You can use keys like those used for the minibuffer history; these work much as they do in the minibuffer, inserting text from prior commands while point remains always at the end of the buffer. You can move through the buffer to previous inputs in their original place, then resubmit them or copy them to the end.

6.3.1 ICS Command History Ring


Fetch the next earlier old ICS command (comint-previous-input).


Fetch the next later old ICS command (comint-next-input).


Begin an incremental regexp search of old ICS commands (comint-history-isearch-backward-regexp).

C-c C-x

Fetch the next subsequent command from the history (comint-get-next-from-history).

C-c .

Fetch one argument from an old ICS command (comint-input-previous-argument).

C-c C-l

Display the buffer’s history of ICS commands in another window (comint-dynamic-list-input-ring).

ICS buffers provide a history of previously entered commands. To reuse commands from the history, use the editing commands M-p, M-n, M-r and M-s. These work just like the minibuffer history commands (see (emacs)Minibuffer History), except that they operate within the ICS buffer rather than the minibuffer.

M-p fetches an earlier ICS command to the end of the ICS buffer. Successive use of M-p fetches successively earlier commands, each replacing any text that was already present as potential input. M-n does likewise except that it finds successively more recent ICS commands from the buffer. C-UP works like M-p, and C-DOWN like M-n.

The history search command M-r begins an incremental regular expression search of previous ICS commands. After typing M-r, start typing the desired string or regular expression; the last matching ICS command will be displayed in the current line. Incremental search commands have their usual effects—for instance, C-s and C-r search forward and backward for the next match (see (emacs)Incremental Search). When you find the desired input, type RET to terminate the search. This puts the input in the command line. Any partial input you were composing before navigating the history list is restored when you go to the beginning or end of the history ring.

Often it is useful to reexecute several successive ICS commands that were previously executed in sequence. To do this, first find and reexecute the first command of the sequence. Then type C-c C-x; that will fetch the following command—the one that follows the command you just repeated. Then type RET to reexecute this command. You can reexecute several successive commands by typing C-c C-x RET over and over.

The command C-c . (comint-input-previous-argument) copies an individual argument from a previous command, like ESC . in Bash. The simplest use copies the last argument from the previous ICS command. With a prefix argument n, it copies the nth argument instead. Repeating C-c . copies from an earlier ICS command instead, always using the same value of n (don’t give a prefix argument when you repeat the C-c . command).

These commands get the text of previous ICS commands from a special history list, not from the ICS buffer itself. Thus, editing the ICS buffer, or even killing large parts of it, does not affect the history that these commands access.

6.3.2 ICS History Copying

C-c C-p

Move point to the previous prompt (comint-previous-prompt).

C-c C-n

Move point to the following prompt (comint-next-prompt).


Copy the input command at point, inserting the copy at the end of the buffer (comint-copy-old-input). This is useful if you move point back to a previous command. After you copy the command, you can submit the copy as input with RET. If you wish, you can edit the copy before resubmitting it. If you use this command on an output line, it copies that line to the end of the buffer.


If comint-use-prompt-regexp is nil (the default), copy the old input command that you click on, inserting the copy at the end of the buffer (comint-insert-input). If comint-use-prompt-regexp is non-nil, or if the click is not over old input, just yank as usual.

Moving to a previous input and then copying it with C-c RET or Mouse-2 produces the same results—the same buffer contents—that you would get by using M-p enough times to fetch that previous input from the history list. However, C-c RET copies the text from the buffer, which can be different from what is in the history list if you edit the input text in the buffer after it has been sent.

6.4 Seeking an opponent for a new game

After you connected to a server, one of the first things you will want to do is find an opponent for a new game. You can use the ICS command ‘seek’ to announce your availability for a chess game to interested people.

For example:

fics% seek 10 10 rated

This will announce your availability to play a rated game with 10 minutes initial time-control for each player, and 10 seconds added for every move made.

6.5 The sought game display

There is a special mode for displaying games sought by other users on an Internet Chess Server. Provided you didn’t turn off seek advertisements manually (for instance by setting the seek variable to 0 (off) on the ICS server by issuing "set seek 0"), the first seek advertisement automatically pops up a new window which is in chess-ics-ads-mode, a derivative of tabulated-list-mode.

Function: chess-ics-ads-mode

A mode for displaying ICS game seek advertisements.

This mode runs the hook chess-ics-ads-mode-hook, as the final step during initialization.

key binding — ——-

? describe-mode ret chess-ics-sought-accept <mouse-2> chess-ics-sought-accept

In this buffer, use mouse-2 or RET on a line to accept that particular game and play it.

6.6 Watching other games

You can also watch other games currently being played on ICS. Even services like ‘LectureBot’ from FICS can be used.

fics% observe lecturebot
You are now observing game 5.
Game 5: LectureBot (0) LectureBot (0) unrated untimed 0 0

LectureBot(TD)(----)[5] kibitzes: (Note: A passed pawn is a pawn that
          does not have enemy pawns blocking the path either on the
          same or adjacent files).
LectureBot(TD)(----)[5] kibitzes: Connected passed pawns are a pain to
          have to deal with. They are usually a winning advantage if
          they cannot be blockaded. The blockading piece has to give
          up duties elsewhere. It's almost like being a piece up.
fics% unobserv lecturebot
Removing game 5 from observation list.

Once you start to observe a particular game or player, the current position will pop up in a chessboard display. As you are an observer, you will not be able to enter new moves. However, you should be able to navigate back and forth in the history of the game.

If a new move is made by any party in the game and you are currently displaying the last position in the game, the chessboard display will automatically update to reflect the new position and show the last move in the mode line.

Appendix A GNU Free Documentation License

Version 1.3, 3 November 2008
Copyright © 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.

Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.

    The purpose of this License is to make a manual, textbook, or other functional and useful document free in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

    This License is a kind of “copyleft”, which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

    We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.


    This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The “Document”, below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as “you”. You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.

    A “Modified Version” of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

    A “Secondary Section” is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document’s overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.

    The “Invariant Sections” are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none.

    The “Cover Texts” are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words.

    A “Transparent” copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not “Transparent” is called “Opaque”.

    Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modification. Examples of transparent image formats include PNG, XCF and JPG. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML, PostScript or PDF produced by some word processors for output purposes only.

    The “Title Page” means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, “Title Page” means the text near the most prominent appearance of the work’s title, preceding the beginning of the body of the text.

    The “publisher” means any person or entity that distributes copies of the Document to the public.

    A section “Entitled XYZ” means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in another language. (Here XYZ stands for a specific section name mentioned below, such as “Acknowledgements”, “Dedications”, “Endorsements”, or “History”.) To “Preserve the Title” of such a section when you modify the Document means that it remains a section “Entitled XYZ” according to this definition.

    The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License.


    You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

    You may also lend copies, under the same conditions stated above, and you may publicly display copies.


    If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document’s license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

    If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.

    If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.

    It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.


    You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:

    1. Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.
    2. List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has fewer than five), unless they release you from this requirement.
    3. State on the Title page the name of the publisher of the Modified Version, as the publisher.
    4. Preserve all the copyright notices of the Document.
    5. Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.
    6. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.
    7. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document’s license notice.
    8. Include an unaltered copy of this License.
    9. Preserve the section Entitled “History”, Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section Entitled “History” in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.
    10. Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the “History” section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.
    11. For any section Entitled “Acknowledgements” or “Dedications”, Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.
    12. Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.
    13. Delete any section Entitled “Endorsements”. Such a section may not be included in the Modified Version.
    14. Do not retitle any existing section to be Entitled “Endorsements” or to conflict in title with any Invariant Section.
    15. Preserve any Warranty Disclaimers.

    If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version’s license notice. These titles must be distinct from any other section titles.

    You may add a section Entitled “Endorsements”, provided it contains nothing but endorsements of your Modified Version by various parties—for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

    You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

    The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.


    You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers.

    The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.

    In the combination, you must combine any sections Entitled “History” in the various original documents, forming one section Entitled “History”; likewise combine any sections Entitled “Acknowledgements”, and any sections Entitled “Dedications”. You must delete all sections Entitled “Endorsements.”


    You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

    You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.


    A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an “aggregate” if the copyright resulting from the compilation is not used to limit the legal rights of the compilation’s users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.

    If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document’s Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.


    Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.

    If a section in the Document is Entitled “Acknowledgements”, “Dedications”, or “History”, the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.


    You may not copy, modify, sublicense, or distribute the Document except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense, or distribute it is void, and will automatically terminate your rights under this License.

    However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.

    Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.

    Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, receipt of a copy of some or all of the same material does not give you any rights to use it.


    The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.

    Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License “or any later version” applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation. If the Document specifies that a proxy can decide which future versions of this License can be used, that proxy’s public statement of acceptance of a version permanently authorizes you to choose that version for the Document.


    “Massive Multiauthor Collaboration Site” (or “MMC Site”) means any World Wide Web server that publishes copyrightable works and also provides prominent facilities for anybody to edit those works. A public wiki that anybody can edit is an example of such a server. A “Massive Multiauthor Collaboration” (or “MMC”) contained in the site means any set of copyrightable works thus published on the MMC site.

    “CC-BY-SA” means the Creative Commons Attribution-Share Alike 3.0 license published by Creative Commons Corporation, a not-for-profit corporation with a principal place of business in San Francisco, California, as well as future copyleft versions of that license published by that same organization.

    “Incorporate” means to publish or republish a Document, in whole or in part, as part of another Document.

    An MMC is “eligible for relicensing” if it is licensed under this License, and if all works that were first published under this License somewhere other than this MMC, and subsequently incorporated in whole or in part into the MMC, (1) had no cover texts or invariant sections, and (2) were thus incorporated prior to November 1, 2008.

    The operator of an MMC Site may republish an MMC contained in the site under CC-BY-SA on the same site at any time before August 1, 2009, provided the MMC is eligible for relicensing.

ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

  Copyright (C)  year  your name.
  Permission is granted to copy, distribute and/or modify this document
  under the terms of the GNU Free Documentation License, Version 1.3
  or any later version published by the Free Software Foundation;
  with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
  Texts.  A copy of the license is included in the section entitled ``GNU
  Free Documentation License''.

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with…Texts.” line with this:

    with the Invariant Sections being list their titles, with
    the Front-Cover Texts being list, and with the Back-Cover Texts
    being list.

If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.

Concept Index

Jump to:   A   B   C   D   E   F   G   H   I   L   M   N   O   P   Q   R   S   T   V   W  
Index Entry  Section

acd’ opcode: Opcode "acd" analysis count depth
acn’ opcode: Opcode "acn" analysis count nodes
acs’ opcode: Opcode "acs" analysis count seconds
AI engine: AI
algebraic notation: Algebraic notation
algebraic notation, entering moves with: Entering moves with algebraic notation
algebraic notation, searching moves: Basic operations
am’ opcode: Opcode "am" avoid move(s)
annotations: Annotations
ASCII diagram display: Plain ASCII diagram displays

bishop: Position coordinates
bm’ opcode: Opcode "bm" best move(s)

chess display mode: Chess display mode
Chess ICS mode: Chess ICS Mode
chess opening books modules: Chess Opening Books
chess session: Chess Session
chess-eco module: ECO Classification
chess-file module: chess-file
chess-images module: Graphical displays
chess-none: The Null Engine
chess-scid module: chess-scid
chessboard display: Chessboard displays
collection: Collections
collection database: Opening Databases
Comint mode: Chess ICS Mode
command history: Command History
command history ring: ICS Command Ring
connecting to internet chess server: Connecting to a server
coordinates: Position coordinates
copying command history: ICS History Copying
crafty: Crafty
creating games: Creating games
creating plies: Creating plies
creating positions: Creating positions
creating variations: Creating variations
customize chess-images display: Graphical displays
customize chess-plain display: Plain ASCII diagram displays
customize ics1 display: ICS1 style ASCII displays

database modules: Database Modules
database, modifying: Modifying Databases
database, opening: Opening Databases
display: Chessboard displays
display manipulation functions: Generic display manipulation functions

east: Position coordinates
ECO classification: ECO Classification
engines: Engines
engines, common functions: Common functions
EPD notation: EPD notation
EPD operations: Operations

FEN notation: FEN notation
figurine algebraic notation: Algebraic notation
fruit: Fruit

game: Games
game plies: Game plies
game positions: Game positions
game tags: Game tags
game, creating: Creating games
glaurung: Glaurung
gnuchess: GNU Chess
graphical display: Graphical displays

history copying: ICS History Copying

ICS1 display: ICS1 style ASCII displays
internet chess servers: Internet Chess Servers

library: The chess.el library
long algebraic notation: Algebraic notation

mode, Comint: Chess ICS Mode
mode, ICS: Chess ICS Mode
modifying databases: Modifying Databases
modules: Modules

north: Position coordinates
northeast: Position coordinates
northwest: Position coordinates
null engine: The Null Engine
numeric notation: Algebraic notation

opcodes: Operations
opening database: Opening Databases

PGN mode: PGN mode
PGN notation: PGN notation
phalanx: Phalanx
ply: Plies
ply details: Ply details
ply, creating: Creating plies
polyglot opening book format: Polyglot opening book format support
position: Positions
position coordinates: Position coordinates
position, creating: Creating positions

queen: Position coordinates
queen: Position coordinates
querying databases: Querying Databases

rook: Position coordinates

seek advertisements: The sought game display
seeking opponents: Seeking an opponent for a new game
short algebraic notation: Algebraic notation
sjeng: Sjeng
sought game display: The sought game display
south: Position coordinates
southeast: Position coordinates
southwest: Position coordinates
standard algebraic notation: Algebraic notation
stockfish: Stockfish

tags: Game tags

variation: Variations
variation plies: Variation plies
variation positions: Variation positions
variation, creating: Creating variations
variation, make a move: Making a move in a variation

watching other games: Watching other games
west: Position coordinates

Jump to:   A   B   C   D   E   F   G   H   I   L   M   N   O   P   Q   R   S   T   V   W  

Function and Variable Index

Jump to:   B   C  
Index Entry  Section

backward-kill-word: Chess ICS Mode

chess: Chess Session
chess-ai-best-move: AI
chess-ai-depth: AI
chess-ai-quiescence-depth: AI
chess-algebraic-regexp: Algebraic notation
chess-algebraic-to-ply: Algebraic notation
chess-coord-to-index: Position coordinates
chess-crafty-path: Crafty
chess-database-filename: Querying Databases
chess-database-modules: Opening Databases
chess-database-open: Opening Databases
chess-database-query: Querying Databases
chess-database-read: Querying Databases
chess-database-read-only-p: Modifying Databases
chess-default-display: Chess Session
chess-default-engine: Chess Session
chess-default-modules: ECO Classification
chess-direction-east: Position coordinates
chess-direction-north: Position coordinates
chess-direction-northeast: Position coordinates
chess-direction-northwest: Position coordinates
chess-direction-south: Position coordinates
chess-direction-southeast: Position coordinates
chess-direction-southwest: Position coordinates
chess-direction-west: Position coordinates
chess-display-active-p: Generic display manipulation functions
chess-display-clear-board: Generic display manipulation functions
chess-display-create: Generic display manipulation functions
chess-display-draw: Basic operations
chess-display-highlight: Generic display manipulation functions
chess-display-highlight-legal: Chess display mode
chess-display-invert: Generic display manipulation functions
chess-display-invert: Basic operations
chess-display-kill-board: Basic operations
chess-display-move: Generic display manipulation functions
chess-display-move-backward: Basic operations
chess-display-move-first: Basic operations
chess-display-move-forward: Basic operations
chess-display-move-last: Basic operations
chess-display-perspective: Generic display manipulation functions
chess-display-position: Generic display manipulation functions
chess-display-quit: Generic display manipulation functions
chess-display-quit: Basic operations
chess-display-resign: Basic operations
chess-display-search-backward: Basic operations
chess-display-search-forward: Basic operations
chess-display-select-piece: Selecting pieces with the keyboard
chess-display-select-piece: Selecting pieces with the mouse
chess-display-set-game: Generic display manipulation functions
chess-display-set-perspective: Generic display manipulation functions
chess-display-set-position: Generic display manipulation functions
chess-display-set-variation: Generic display manipulation functions
chess-display-update: Generic display manipulation functions
chess-display-yank-board: Basic operations
chess-engine-command: Common functions
chess-engine-create: Common functions
chess-engine-position: Common functions
chess-engine-send: Common functions
chess-engine-set-option: Common functions
chess-epd-read-file: EPD notation
chess-epd-to-pos: EPD notation
chess-fen-to-pos: FEN notation
chess-fischer-random-position: Creating positions
chess-fruit-path: Fruit
chess-game-add-hook: Games
chess-game-add-ply: Games
chess-game-create: Creating games
chess-game-del-tag: Game tags
chess-game-hooks: Games
chess-game-index: Game positions
chess-game-move: Making a move
chess-game-plies: Games
chess-game-ply: Game plies
chess-game-pos: Game positions
chess-game-remove-hook: Games
chess-game-run-hooks: Games
chess-game-seq: Game positions
chess-game-set-hooks: Games
chess-game-set-plies: Games
chess-game-set-tag: Game tags
chess-game-set-tags: Game tags
chess-game-side-to-move: Game positions
chess-game-tag: Game tags
chess-game-tags: Game tags
chess-game-to-pgn: PGN notation
chess-glaurung-path: Glaurung
chess-gnuchess-path: GNU Chess
chess-ics: Connecting to a server
chess-ics-ads-mode: The sought game display
chess-ics-server-list: Internet Chess Servers
chess-ics1-separate-frame: ICS1 style ASCII displays
chess-images-directory: Graphical displays
chess-images-separate-frame: Graphical displays
chess-index-file: Position coordinates
chess-index-rank: Position coordinates
chess-index-to-coord: Position coordinates
chess-input-shortcut: Entering moves with algebraic notation
chess-input-shortcut-delete: Entering moves with algebraic notation
chess-legal-plies: Creating plies
chess-next-index: Position coordinates
chess-pgn-insert-plies: PGN notation
chess-pgn-to-game: PGN notation
chess-pgn-visualize: PGN mode
chess-phalanx-path: Phalanx
chess-plain-black-square-char: Plain ASCII diagram displays
chess-plain-border-style: Plain ASCII diagram displays
chess-plain-piece-chars: Plain ASCII diagram displays
chess-plain-separate-frame: Plain ASCII diagram displays
chess-plain-spacing: Plain ASCII diagram displays
chess-plain-upcase-indicates: Plain ASCII diagram displays
chess-plain-white-square-char: Plain ASCII diagram displays
chess-ply-changes: Ply details
chess-ply-create: Creating plies
chess-ply-final-p: The "next" position
chess-ply-keyword: Polyglot opening book format support
chess-ply-next-pos: The "next" position
chess-ply-pos: Ply details
chess-ply-set-changes: Ply details
chess-ply-set-pos: Ply details
chess-ply-source: Ply details
chess-ply-target: Ply details
chess-ply-to-algebraic: Algebraic notation
chess-polyglot-book: Polyglot opening book format support
chess-polyglot-book-file: Polyglot opening book format support
chess-polyglot-book-open: Polyglot opening book format support
chess-polyglot-book-plies: Polyglot opening book format support
chess-polyglot-book-ply: Polyglot opening book format support
chess-polyglot-book-strength: Polyglot opening book format support
chess-pos-add-annotation: Annotations
chess-pos-always-white: Position details
chess-pos-annotations: Annotations
chess-pos-can-castle: Position details
chess-pos-copy: Creating positions
chess-pos-create: Creating positions
chess-pos-en-passant: Position details
chess-pos-move: Position details
chess-pos-passed-pawns: Position details
chess-pos-piece: Position details
chess-pos-piece-p: Position details
chess-pos-search: Position details
chess-pos-search*: Position details
chess-pos-set-can-castle: Position details
chess-pos-set-en-passant: Position details
chess-pos-set-piece: Position details
chess-pos-set-side-to-move: Position details
chess-pos-set-status: Position details
chess-pos-side-to-move: Position details
chess-pos-status: Position details
chess-pos-to-epd: EPD notation
chess-pos-to-fen: FEN notation
chess-rf-to-index: Position coordinates
chess-search-position: Position details
chess-sjeng-path: Sjeng
chess-starting-position: Creating positions
chess-starting-position: FEN notation
chess-stockfish-path: Stockfish
chess-var-add-ply: Making a move in a variation
chess-var-create: Creating variations
chess-var-index: Variation positions
chess-var-move: Making a move in a variation
chess-var-plies: Variation plies
chess-var-ply: Variation plies
chess-var-pos: Variation positions
chess-var-seq: Variation positions
chess-var-side-to-move: Variation positions
chess-var-to-algebraic: Variation plies
comint-accumulate: Chess ICS Mode
comint-bol-or-process-mark: Chess ICS Mode
comint-buffer-maximum-size: Chess ICS Mode
comint-copy-old-input: ICS History Copying
comint-delchar-or-maybe-eof: Chess ICS Mode
comint-delete-output: Chess ICS Mode
comint-dynamic-list-input-ring: ICS Command Ring
comint-get-next-from-history: ICS Command Ring
comint-history-isearch-backward-regexp: ICS Command Ring
comint-input-previous-argument: ICS Command Ring
comint-kill-input: Chess ICS Mode
comint-next-input: ICS Command Ring
comint-next-prompt: ICS History Copying
comint-previous-input: ICS Command Ring
comint-previous-prompt: ICS History Copying
comint-send-input: Chess ICS Mode
comint-show-maximum-output: Chess ICS Mode
comint-show-output: Chess ICS Mode
comint-truncate-buffer: Chess ICS Mode
comint-write-output: Chess ICS Mode

Jump to:   B   C  

Key Index

Jump to:   ,   .   1   2   3   4   5   6   7   8   <   =   >  
A   B   C   D   E   F   G   H   K   M   N   Q   R   T   X  
Index Entry  Section

,: Basic operations

.: Basic operations

1: Entering moves with algebraic notation

2: Entering moves with algebraic notation

3: Entering moves with algebraic notation

4: Entering moves with algebraic notation

5: Entering moves with algebraic notation

6: Entering moves with algebraic notation

7: Entering moves with algebraic notation

8: Entering moves with algebraic notation

<: Basic operations

=: Entering moves with algebraic notation

>: Basic operations

a: Entering moves with algebraic notation

b: Entering moves with algebraic notation
B: Entering moves with algebraic notation
backspace: Entering moves with algebraic notation

c: Entering moves with algebraic notation
C-c .: ICS Command Ring
C-c C-a: Chess ICS Mode
C-c C-d: Basic operations
C-c C-e: Chess ICS Mode
C-c C-l: ICS Command Ring
C-c C-n: ICS History Copying
C-c C-o: Chess ICS Mode
C-c C-p: ICS History Copying
C-c C-r: Basic operations
C-c C-r: Chess ICS Mode
C-c C-s: Chess ICS Mode
C-c C-u: Chess ICS Mode
C-c C-w: Chess ICS Mode
C-c C-x: ICS Command Ring
C-c RET: ICS History Copying
C-c SPC: Chess ICS Mode
C-d: Chess ICS Mode
C-i: Basic operations
C-M-l: Chess ICS Mode
C-r: Basic operations
C-s: Basic operations
C-u M-w: Basic operations
C-u M-x chess RET: Chess Session
C-u M-x chess RET ai RET: AI
C-u M-x chess RET crafty RET: Crafty
C-u M-x chess RET fruit RET: Fruit
C-u M-x chess RET glaurung RET: Glaurung
C-u M-x chess RET gnuchess RET: GNU Chess
C-u M-x chess RET none RET: The Null Engine
C-u M-x chess RET phalanx RET: Phalanx
C-u M-x chess RET sjeng RET: Sjeng
C-u M-x chess RET stockfish RET: Stockfish
C-y: Basic operations

d: Entering moves with algebraic notation
down-mouse-1: Selecting pieces with the mouse
down-mouse-2: Selecting pieces with the mouse
drag-mouse-1: Selecting pieces with the mouse
drag-mouse-2: Selecting pieces with the mouse

e: Entering moves with algebraic notation

f: Entering moves with algebraic notation

g: Entering moves with algebraic notation

h: Entering moves with algebraic notation

K: Entering moves with algebraic notation

M-n: ICS Command Ring
M-p: ICS Command Ring
M-r: ICS Command Ring
M-w: Basic operations
M-x chess RET: Chess Session
M-x customize-group RET chess-ics1 RET: ICS1 style ASCII displays
M-x customize-group RET chess-images RET: Graphical displays
M-x customize-group RET chess-plain RET: Plain ASCII diagram displays

N: Entering moves with algebraic notation

Q: Entering moves with algebraic notation

R: Entering moves with algebraic notation
RET: Selecting pieces with the keyboard
RET: Chess ICS Mode
RET: The sought game display

TAB: Basic operations

X: Basic operations
x: Entering moves with algebraic notation

Jump to:   ,   .   1   2   3   4   5   6   7   8   <   =   >  
A   B   C   D   E   F   G   H   K   M   N   Q   R   T   X