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precalculated [[Endgame|endgame]] [https://en.wikipedia.org/wiki/Table_%28database%29 tables] generated by an exhaustive [[Retrograde Analysis|retrograde analysis]]. During its [[Chess Game|game play]] and/or [[Search|search]], [[Interior Node Recognizer|recognizing]] a specific [[Material|material composition]], a chess program can probe, or in principle compute these tables to determine the outcome of positions definitively and act as an [[Oracle|oracle]] providing the optimal moves. The tables are usually divided into separate [https://en.wikipedia.org/wiki/Computer_file files] for each material configuration and [[Side to move|side to move]]. What all different [[Endgame Tablebases#Formats|formats]] of tablebases have in common is that every possible piece placement has its own, unique index number which represents the position where the information about the position is located in the file. Positions with non-null castling rights could be represented in an EGT EGTB but typically are not.

An EGTB is a set of endgames. Each endgame is a set of records about positions’ information. All involving positions of that in an endgamemust have the same material. Each Typically each position has 's record associates with an integer number which informs how far that position is from mating/being mated or converting, (depends on the type of its metrics).  Based on values of those integer numbers it can answer directly two questions of the EGTB: 1) for a given position it is a draw or a win/loss position and 2) how far it is from mating/being mated or converting. To answer the 3rd question, the best move of a position can be indirectly calculated: generate all legal moves, make them, probe all new positions, compare probing scores for the highest one and the associated move is the best one. Theoretically, we can add more information to each position’s record. However, due to large numbers of involving positions, any additional information may make the whole EGTB becomes significantly larger. Thus so far none of popular EGTBs store any extra information and their records actually contain those integers only. All numbers records of an endgame are simply organized as an two arrays (one array of integersfor one side/color). In other words, each item in that array those arrays is an integer and its index on an array is mapped to a unique position. For a given chess position, we will calculate its index then access its data record/integer via that index without searching.

The array ==Endgame files==Those arrays of an endgame can be stored in files. Typically each array is stored in one file. However, sometimes they can be combined into one larger file or splitted into more files to easier copy or a few manage. Those files, may be in none compressed or uncompressed forms. If they are compressed formats, they are typically divided and compressed by small blocks thus they don't need to load and decompress all data to extract just a position.  ==In memory==Some chess engines create themselves EGTBs on-flight and keep all data in memory without saving/loading to files. Due to limit by initial time they can generate and use very small EGTBs only. ==Sizes==The size of an endgame depends on:* The number of involving pieces: more pieces, the bigger size* Type of pieces: for standard chess, more Pawns is the smaller size* Type of metric* The largest value: the integer number should be large enough to cover the largest value. Different endgames will have different largest values. Thus some endgames need only one byte per item but some need 2 bytes* Indexing: The algorithms to map between an array item and a position* Compress ratio So far the size of an EGTB is the most important factor of success.

* [[Christoph Wirth]], [[Jürg Nievergelt]] ('''1999'''). ''Exhaustive and Heuristic Retrograde Analysis of the KPPKP Endgame.'' [[ICGA Journal#22_2|ICCA Journal, Vol. 22, No. 2]]<ref>[http://kirill-kryukov.com/chess/discussion-board/viewtopic.php?f=6&t=2923 Chris Wirth's endgame tablebases] by [[Denis Mendoza|Denis P. Mendoza]], [[Computer Chess Forums|CCRL Endgame Tablebases]], December 13, 2007 » [[Chessterfield]]</ref>

* [[Ulrich Thiemonds]] ('''1999'''). ''Ein regelbasiertes Spielprogramm für Schachendspiele''. [https://en.wikipedia.org/wiki/University_of_Bonn University of Bonn], Diploma Diplom thesis, [httphttps://www.iaiidb.uni-bonn.de/~idbpublications/diplomarbeitenda/thiemonds99.psda_thiemonds_1999.gz zipped pspdf pdf] (German)

* [https://www.chessdb.cn/queryc_en/ Chess Cloud Database Query Interface] by [[Bojun Guo|noobpwnftw]] [[Syzygy Bases|Syzygy]] DTZ50 probing