Answers.Body: <p>It looks to me like someone just went in order of these started with the b pawn, the c pawn, the d pawn, the e pawn, and then indexed those. and then went the other side and said these were responded to by the b pawn, the c pawn, the d pawn.</p>
  
  <p>Naturally, there is a more sophisticated classification of the whole deal. ECO stands for the Encyclopedia of Chess Openings. As with all encyclopedias, it has volumes. There are 5 volumes: A, B, C, D, E. Note that these correlate to the range of eco's which is A00 to E99. In your example, there are 40 entries for the Ruy Lopez (C60 through C99).</p>
  
  <p>Each volume is broken down into a type of openings designated by, </p>
  
  <p><li>Volume A: <a href="http://en.wikipedia.org/wiki/Flank_opening" rel="nofollow noreferrer">Flank Openings</a>
  <li>Volume B: <a href="http://en.wikipedia.org/wiki/Semi-Open_Game" rel="nofollow noreferrer">Semi-Open Games</a> other than the French Defense
  <li>Volume C: <a href="http://en.wikipedia.org/wiki/Open_Game" rel="nofollow noreferrer">Open Games</a> and the French Defense
  <li>Volume D: <a href="http://en.wikipedia.org/wiki/Closed_Game" rel="nofollow noreferrer">Closed Games</a> and <a href="http://en.wikipedia.org/wiki/Semi-Closed_Game" rel="nofollow noreferrer">Semi-Closed Games</a>
  <li>Volume E: <a href="http://en.wikipedia.org/wiki/Indian_Defense" rel="nofollow noreferrer">Indian Defenses</a></p>
  
  <p>and in general, the main eco codes break down into</p>
  
  <p><strong>A</strong>
  <li>White first moves other than 1.e4, 1.d4 (A00–A39)
  <li>1.d4 without 1...d5, 1...Nf6: Atypical replies to 1.d4 (A40–A44)
  <li>1.d4 Nf6 without 2.c4: Atypical replies to 1...Nf6 (A45–A49)
  <li>1.d4 Nf6 2.c4 without 2...e6, 2...g6: Atypical Indian systems (A50–A79)
  <li>1.d4 f5: Dutch Defence (A80–A99)</p>
  
  <p><strong>B</strong>
  <li>1.e4 without 1...c5, 1...e6, 1...e5 (B00–B09)
  <li>1.e4 c6: Caro-Kann Defence (B10–B19)
  <li>1.e4 c5: Sicilian Defence (B20–B99)</p>
  
  <p><strong>C</strong>
  <li>1.e4 e6: French Defence (C00–C19)
  <li>1.e4 e5: Double King Pawn games (C20–C99)</p>
  
  <p><strong>D</strong>
  <li>1.d4 d5: Double Queen Pawn games (D00–D69)
  <li>1.d4 Nf6 2.c4 g6 with 3...d5: Grünfeld Defence (D70–D99)</p>
  
  <p><strong>E</strong>
  <li>1.d4 Nf6 2.c4 e6: Indian systems with ...e6 (E00–E59)
  <li>1.d4 Nf6 2.c4 g6 without 3...d5: Indian systems with ...g6 (except Grünfeld) (E60–E99)</p>
  
  <p><em>Source:</em> <a href="http://en.wikipedia.org/wiki/Encyclopaedia_of_Chess_Openings" rel="nofollow noreferrer">http://en.wikipedia.org/wiki/Encyclopaedia_of_Chess_Openings</a></p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2013-01-09T09:26:58.747Z
Answers.LastActivityDate: 2016-12-27T15:07:48.907Z
Answers.LastEditDate: 2016-12-27T15:07:48.907Z
Answers.UserDisplayName: Travis J
Answers.Body: <p>The origin of the Classification and the Codes themselves were the <a href="https://en.wikipedia.org/wiki/Encyclopaedia_of_Chess_Openings" rel="nofollow noreferrer">Encyclopedia of Chess Openings</a> compiled and edited by Aleksandar Matanović.</p>
  
  <p>They are organized as indicated in another answer above as were originally laid out in the ECO.  For a fairly comprehensive <strong>oneline</strong> copy of Chess Openings see <a href="http://www.365chess.com/eco.php" rel="nofollow noreferrer">HERE</a></p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2016-12-26T23:50:47.187Z
Answers.LastActivityDate: 2016-12-26T23:50:47.187Z
Answers.UserDisplayName: user34445
Body: <p>As an example, I will use the <code>Ruy Lopez</code>.</p>
  
  <p><code>C60</code> is defined as <code>1.e4 e5 2.Nf3 Nc6 3.Bb5</code> as well as host of other <code>Ruy Lopez</code> variations.</p>
  
  <p><code>C60</code> is also the <code>Ruy Lopez - Cozio Defence, Paulsen Variation</code> which is defined by the moves <code>1.e4 e5 2.Nf3 Nc6 3.Bb5 Nge7 4.Nc3 g6</code></p>
  
  <p><code>C66</code> is the 'Ruy Lopez - Closed Berlin Defence, Chigorin Variation<code>which is defined by the moves</code>1.e4 e5 2.Nf3 Nc6 3.Bb5 Nf6 4.O-O d6 5.d4 Nd7`</p>
  
  <p>How do these codes get assigned?  In the case of the <code>Ruy Lopez</code>, are the codes differentiated after the move <code>3.Bb5</code>?</p>
  
Tags: <opening>
Title: How are the ECO codes for chess openings assigned?
ThreadText: # How are the ECO codes for chess openings assigned?
  
  (Asked by: username_0 on 2013-01-09)
  
  As an example, I will use the `Ruy Lopez`.
  
  `C60` is defined as `1.e4 e5 2.Nf3 Nc6 3.Bb5` as well as host of other `Ruy Lopez` variations.
  
  `C60` is also the `Ruy Lopez - Cozio Defence, Paulsen Variation` which is defined by the moves `1.e4 e5 2.Nf3 Nc6 3.Bb5 Nge7 4.Nc3 g6`
  
  `C66` is the 'Ruy Lopez - Closed Berlin Defence, Chigorin Variation`which is defined by the moves`1.e4 e5 2.Nf3 Nc6 3.Bb5 Nf6 4.O-O d6 5.d4 Nd7`
  
  How do these codes get assigned? In the case of the `Ruy Lopez`, are the codes differentiated after the move `3.Bb5`?
  
  **Tags:** opening
  
  
  ---
  
  ## 2 answers
  
  ### Answer by username_1 on 2013-01-09. Score: 5 | Accepted answer
  
  It looks to me like someone just went in order of these started with the b pawn, the c pawn, the d pawn, the e pawn, and then indexed those. and then went the other side and said these were responded to by the b pawn, the c pawn, the d pawn.
  
  Naturally, there is a more sophisticated classification of the whole deal. ECO stands for the Encyclopedia of Chess Openings. As with all encyclopedias, it has volumes. There are 5 volumes: A, B, C, D, E. Note that these correlate to the range of eco's which is A00 to E99. In your example, there are 40 entries for the Ruy Lopez (C60 through C99).
  
  Each volume is broken down into a type of openings designated by,
  
  - Volume A: [Flank Openings](http://en.wikipedia.org/wiki/Flank_opening)- Volume B: [Semi-Open Games](http://en.wikipedia.org/wiki/Semi-Open_Game) other than the French Defense- Volume C: [Open Games](http://en.wikipedia.org/wiki/Open_Game) and the French Defense- Volume D: [Closed Games](http://en.wikipedia.org/wiki/Closed_Game) and [Semi-Closed Games](http://en.wikipedia.org/wiki/Semi-Closed_Game)- Volume E: [Indian Defenses](http://en.wikipedia.org/wiki/Indian_Defense)
  
  and in general, the main eco codes break down into
  
  **A**- White first moves other than 1.e4, 1.d4 (A00–A39)- 1.d4 without 1...d5, 1...Nf6: Atypical replies to 1.d4 (A40–A44)- 1.d4 Nf6 without 2.c4: Atypical replies to 1...Nf6 (A45–A49)- 1.d4 Nf6 2.c4 without 2...e6, 2...g6: Atypical Indian systems (A50–A79)- 1.d4 f5: Dutch Defence (A80–A99)
  
  **B**- 1.e4 without 1...c5, 1...e6, 1...e5 (B00–B09)- 1.e4 c6: Caro-Kann Defence (B10–B19)- 1.e4 c5: Sicilian Defence (B20–B99)
  
  **C**- 1.e4 e6: French Defence (C00–C19)- 1.e4 e5: Double King Pawn games (C20–C99)
  
  **D**- 1.d4 d5: Double Queen Pawn games (D00–D69)- 1.d4 Nf6 2.c4 g6 with 3...d5: Grünfeld Defence (D70–D99)
  
  **E**- 1.d4 Nf6 2.c4 e6: Indian systems with ...e6 (E00–E59)- 1.d4 Nf6 2.c4 g6 without 3...d5: Indian systems with ...g6 (except Grünfeld) (E60–E99)
  
  *Source:* <http://en.wikipedia.org/wiki/Encyclopaedia_of_Chess_Openings>
  
  
  ---
  
  ### Answer by username_2 on 2016-12-26. Score: 0
  
  The origin of the Classification and the Codes themselves were the [Encyclopedia of Chess Openings](https://en.wikipedia.org/wiki/Encyclopaedia_of_Chess_Openings) compiled and edited by Aleksandar Matanović.
  
  They are organized as indicated in another answer above as were originally laid out in the ECO. For a fairly comprehensive **oneline** copy of Chess Openings see [HERE](http://www.365chess.com/eco.php)
  
  
  ---
  
  