Editing Universal Chess Interface

{{short description|Communication protocol for chess software}}
The '''Universal Chess Interface''' ('''UCI''') is an open [[communication protocol]] that enables [[chess engine]]s to communicate with [[user interface]]s.<ref name="bwor_Busi">{{Cite web| title = Chess engines| work = Business World Online| date = 2017-04-06| access-date = 2018-06-14| url = http://www.bworldonline.com/content.php?id=143346}}</ref><ref name="slas_Lich">{{Cite web| title = Lichess embraces blind players with new chess site features| author = Torres, JC| work = SlashGear| date = 2014-06-23| access-date = 2018-06-14| url = https://www.slashgear.com/lichess-embraces-blind-players-with-new-chess-site-features-23334731/}}</ref>

==History==
In November 2000, the UCI protocol was released. Designed by Rudolf Huber and [[Stefan Meyer-Kahlen]], the author of [[Shredder (chess)|Shredder]], UCI rivals the older "Chess Engine Communication Protocol" introduced with [[XBoard|XBoard/WinBoard]].

In 2002, [[Chessbase]], the chess software company which markets [[Fritz (chess)|Fritz]], began to support UCI, which had previously been supported by only a few interfaces and engines.

{{As of|2021}}, well over 300 engines are known to directly support UCI.

==Design==
By design, UCI assigns some tasks to the user interface (i.e., presentation layer) which have traditionally been handled by the engine (at the business layer) itself.{{citation needed|date=July 2016}}

Most notably, the [[opening book]] is usually expected to be handled by the [[User interface|UI]], by simply selecting moves to play until it is out of book, and only then starting up the engine for calculation in the resulting position. UCI does not specify any on-disk format for the opening book. Different UIs usually have their own proprietary formats.{{citation needed|date=July 2016}}

While the UI can also take responsibility for handling [[endgame tablebase]]s, this is arguably better handled in the engine itself, as having tablebase information can be useful for considering possible future positions.<ref>{{cite book|title=Chess Life|url=https://books.google.com/books?id=w2JLAAAAYAAJ|year=2003|publisher=United States Chess Federation}}</ref>

Stefan-Meyer Kahlen's UCI protocol in Shredder uses a variation of [[Algebraic notation (chess)#Long algebraic notation|long algebraic notation]] for moves. A "nullmove" from an engine to a GUI should be sent as 0000.<ref name="wbec_UCIp">{{Cite web| title = UCI protocol| work = www.wbec-ridderkerk.nl| access-date = 2018-06-14| url = http://www.wbec-ridderkerk.nl/html/UCIProtocol.html}}</ref>

;Examples:
*e2e4
*e7e5
*e1g1 (white short castling)
*e7e8q (for promotion)

==Features==
The uci_limitstrength parameter tells engines with this feature to play at a lower level.  The uci_elo parameter specifies the [[Elo rating system|Elo rating]] at which the engine will aim to play.  Engines that have implemented uci_elo include [[Delfi (chess)|Delfi]], [[Fritz (chess)|Fritz]], [[Hiarcs]], [[Houdini (chess)|Houdini]], [[Junior (chess program)|Junior]], [[Rybka]], [[Shredder (software)|Shredder]], [[Sjeng (software)|Sjeng]] and [[Stockfish (chess)|Stockfish]].

==Variants==
The UCI has been modified to play some other games, and [[chess variant]]s. Some of these are:<ref name=evert>{{cite web |last1=Evert |title=UCI protocol for chess variants |url=http://www.talkchess.com/forum3/viewtopic.php?t=54167 |website=TalkChess.com}}</ref>
* Universal Shogi Interface (USI), a dialect for [[shogi]];<ref>{{cite web |title=The Universal Shogi Interface (USI) |url=http://hgm.nubati.net/usi.html |website=hgm.nubati.net}}</ref>
* Universal Chinese Chess Interface (UCCI), a dialect for [[xiangqi]].<ref>{{cite web |title=中国象棋电脑应用规范(五)：中国象棋通用引擎协议 |url=https://www.xqbase.com/protocol/cchess_ucci.htm |website=www.xqbase.com}}</ref>

Each of these protocols may also define variants of [[Portable Game Notation|Portable Game Notation (PGN)]] and [[Forsyth–Edwards_Notation|Forsyth–Edwards Notation (FEN)]]. The XBoard CECP is said to require far fewer changes to support variants.<ref name=evert/>

== See also ==
*[[Chess Engine Communication Protocol]] (XBoard protocol)
*[[Shredder (chess)|Shredder]]
*[[XBoard]]

==References==
{{reflist}}

== External links ==
*[https://www.chessprogramming.org/Category:UCI List of UCI Engines (continuously updated)]
*[https://www.shredderchess.com/chess-info/features/uci-universal-chess-interface.html UCI technical specification download page]

[[Category:Computer chess]]

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