ABK

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ABK, (Arena's book format) the opening book format of Arena. It persists a book tree as array of entries, each entry referring one book move with priority and statistics, an entry index of the next move inside a book line (> 0 if any), and an entry index of a possible sibling move (>= 0 if any). The sizeof of an entry is 28, the initial position indexed by 900.

=Entry Structure= The array of entries/structures is written to / read from a binary file under Windows (x86), struct and integers implicitely stored little-endian wise: struct SBookMoveEntry { char from;     /* a1 0, b1 1, ..., h1 7, ... h8 63 */ char to;       /* a1 0, b1 1, ..., h1 7, ... h8 63 */ char promotion; /* 0 none, +-1 rook, +-2 knight, +-3 bishop, +-4 queen */ char priority; int ngames; int nwon; int nlost; int plycount; int nextMove; int nextSibling; } * pOpeningBook; =Sample Tree= root index ▼ ┌───────────┐                                 ┌───────────┐  │nextSibling│ ─────────────── ► ────────────── │nextSibling│ ─────────────── ► ... ├───────────┤                                  ├───────────┤ │  e2-e4   │                                  │   d2-d4   │ ├───────────┤                                 ├───────────┤  │ nextMove  │                                  │ nextMove  │ └───────────┘                                 └───────────┘        ▼                                              ▼ ┌───────────┐ ┌───────────┐ ┌───────────┐      ┌───────────┐ ┌───────────┐ ┌───────────┐ ┌───────────┐     ┌───────────┐ │nextSibling│►│nextSibling│►│nextSibling│►... │nextSibling│►│nextSibling│►│nextSibling│►│nextSibling│►...►│nextSibling│ ├───────────┤ ├───────────┤ ├───────────┤     ├───────────┤ ├───────────┤ ├───────────┤ ├───────────┤     ├───────────┤ │   e7-e5   │ │   c7-c5   │ │   e6-e6   │      │   d7-d5   │ │   g8-f6   │ │   c7-c6   │ │   e7-e6   │     │   f7-f5   │ ├───────────┤ ├───────────┤ ├───────────┤     ├───────────┤ ├───────────┤ ├───────────┤ ├───────────┤     ├───────────┤ │ nextMove  │ │ nextMove  │ │ nextMove  │      │ nextMove  │ │ nextMove  │ │ nextMove  │ │ nextMove  │     │ nextMove  │ └───────────┘ └───────────┘ └───────────┘     └───────────┘ └───────────┘ └───────────┘ └───────────┘     └───────────┘       ▼             ▼             ▼                  ▼             ▼             ▼              ▼                ▼ ┌───────────┐      ...      ┌───────────┐      ┌───────────┐      ...           ...      ┌───────────┐          ... │nextSibling│►...           │nextSibling│►...  │nextSibling│►...                         │nextSibling│►... ├───────────┤              ├───────────┤      ├───────────┤                             ├───────────┤ │   g1-f3   │               │   d2-d4   │      │   c2-c4   │                             │   e2-e4   │ ├───────────┤              ├───────────┤      ├───────────┤                             ├───────────┤ │ nextMove  │               │ nextMove  │      │ nextMove  │                             │ nextMove  │ └───────────┘              └───────────┘      └───────────┘                             └───────────┘      ▼                            ▼                  ▼                                         ▼	...                          ...                ...                                       ... =See also=
 * CTG - ChessBase book format
 * BIN - Polyglot book format

=Forum Posts=

2007 ...

 * Which is the best general purpose Arena (abk format) Book by Christopher Conkie, CCC, June 04, 2007
 * Opening books format by James Constance, CCC, April 14, 2008
 * Re: Opening books format by Jury Osipov, CCC, April 15, 2008
 * Re: Opening books format by Richard Pijl, CCC, April 15, 2008
 * Re: Opening books format by Dann Corbit, CCC, April 15, 2008
 * Re: Opening books format by Lance Perkins, CCC, April 17, 2008

2010 ...

 * Convert .obk books to .abk books? by David Dahlem, CCC, September 15, 2011
 * Scid / Scid vs. PC - ChessBase (.ctg) and Arena (.abk) by Norbert Raimund Leisner, CCC, August 19, 2016 » CTG, SCID, Scid vs. PC
 * How to use Arena book? by P. Kumar, CCC, February 01, 2017

2020 ...

 * abk to pgn tool by Fauzi, FishCooking, September 14, 2020 » PGN

=External Links=
 * Arena Chess GUI - Opening Books
 * Commercial Opening Book Fauzi 4.5.abk by Fauzi Akram Dabat
 * Free Opening Book Downloads from HIARCS Chess Software
 * Arena opening books from Numpty chess

=References= Up one Level