Editing Encyclopaedia of Chess Openings (section)

==Overview==
Both ''ECO'' and ''[[Chess Informant]]'' are published by the [[Belgrade]]-based company [[Chess Informant|Šahovski Informator]]. The moves are taken from thousands of master games and from published analysis in ''Informant'' and compiled by the editors, most of whom are [[Grandmaster (chess)|grandmasters]], who select the lines which they consider most relevant or critical. The chief editor since the first edition has been [[Aleksandar Matanović]] (1930-2023). The openings are provided in an [[chess opening theory table|''ECO'' table]] that concisely presents the opening lines considered most critical by the editors. ''ECO'' covers the openings in more detail than rival single volume publications such as ''[[Modern Chess Openings]]'' and ''[[Nunn's Chess Openings]]'', but in less detail than specialized opening books.

The books are intended for an international audience and contain only a small amount of text, which is in several languages. The bulk of the content consists of diagrams of positions and chess moves, annotated with [[Chess annotation symbols|symbols]], many of them developed by Chess Informant. [[Chess Informant]] pioneered the use of [[Algebraic notation (chess)#Naming the pieces|Figurine Algebraic Notation]] to avoid the use of initials for the names of the pieces, which vary between languages.

Instead of the traditional names for the openings, ''ECO'' has developed a coding system that has also been adopted by other [[chess publications]]. There are five main categories, "A" to "E", corresponding to the five volumes of the earlier editions, each of which is further subdivided into 100 subcategories, for a total of 500 codes. The term "''ECO''" is often used as a shorthand for this coding system. ''ECO'' code is a registered trademark of [[Chess Informant]].