# ECO openings classification

Scid can classify chess games according to the ECO (Encyclopedia of Chess Openings) chess openings classification. An standard ECO code consists of a letter (A..E) followed by two digits, so there are 500 distinct standard ECO codes.

### Scid extensions to the ECO system

The ECO system is very limited and not sufficient for modern games: some of the 500 codes are almost never seen any more, while some are seen very often. To improve this situation, Scid allows an optional extension to the basic ECO codes: each code can be extended with a letter (a..z), with a further extension (another digit, 1..4) being possible but not used in the standard Scid ECO file yet. So an extended Scid ECO code looks like "A41e" or "E99b2". Many of the most common ECO codes found in modern master-level games have extensions defined in the Scid ECO file.

### The ECO Browser window

The ECO Browser window shows you the positions that are used to classify each ECO code, and the frequency and performance of ECO codes in the current database.

The upper pane shows the frequency of each ECO code in the current database. The bars in the graph have three sections: the lowest (lightest color) is the number of White wins, the middle is the number of draws, and the highest (darkest) is the number of Black wins. This lets you see at a glance the characteristics of an opening: for example, if White is scoring very well, or if draws are very common.

To go to a deeper ECO level, click the left mouse button on a bar in the graph (or type the letter or digit it corresponds to). To go back to the higher level, click the right mouse button anywhere in the graph, or press the left arrow (or delete or backspace) key.

The lower pane shows the positions that comprise a particular ECO code, according to the ECO file you have loaded.

### Loading the Scid ECO file

The ECO file that comes with Scid is called scid.eco, and Scid tries to load this when it starts up. If Scid cannot find it, you will need to do the following to enable ECO classification:

- (a) In Scid, use the menu command [Options: Load ECO file] and select the file scid.eco.
- (b) Save options (from the [Options] menu).

After you do this, the ECO file will be loaded every time you start Scid.

### ECO code system

The basic structure of the ECO system is:

A 1.d4 Nf6 2...; 1.d4 ...; 1.c4; 1.various

- A0 1.various (A02-A03 1.f4: Bird's Opening, A04-A09 1.Nf3: Reti, King's Indian Attack)
- A1 1.c4 ...: English
- A2 1.c4 e5: King's English
- A3 1.c4 c5: English, Symmetrical
- A4 1.d4 ...: Queen's Pawn
- A5 1.d4 Nf6 2.c4 ..: Indian Defence
- A6 1.d4 Nf6 2.c4 c5 3.d5 e6: Modern Benoni
- A7 A6 + 4.Nc3 exd5 5.cxd5 d6 6.e4 g6 7.Nf3
- A8 1.d4 f5: Dutch Defence
- A9 1.d4 f5 2.c4 e6: Dutch Defence

B 1.e4 c5; 1.e4 c6; 1.e4 d6; 1.e4 various

- B0 1.e4 ... (B02-B05 1.e4 Nf6: Alekhine Defence; B07-B09 1.e4 d6: Pirc)
- B1 1.e4 c6: Caro-Kann
- B2 1.e4 c5: Sicilian Defence
- B3 1.e4 c5 2.Nf3 Nc6: Sicilian
- B4 1.e4 c5 2.Nf3 e6: Sicilian
- B5 1.e4 c5 2.Nf3 d6: Sicilian
- B6 B5 + 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 Nc6
- B7 B5 + 4.Nxd4 Nf6 5.Nc3 g6: Sicilian Dragon
- B8 B5 + 4.Nxd4 Nf6 5.Nc3 e6: Sicilian Scheveningen
- B9 B5 + 4.Nxd4 Nf6 5.Nc3 a6: Sicilian Najdorf

C 1.e4 e5; 1.e4 e6

- C0 1.e4 e6: French Defence
- C1 1.e4 e6 2.d4 d5 3.Nc3: French, Winawer/Classical
- C2 1.e4 e5: Open Game
- C3 1.e4 e5 2.f4: King's Gambit
- C4 1.e4 e5 2.Nf3: Open Game
- C5 1.e4 e5 2.Nf3 Nc6 3.Bc4: Italian; Two Knights
- C6 1.e4 e5 2.Nf3 Nc6 3.Bb5: Spanish (Ruy Lopez)
- C7 1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4: Spanish
- C8 C7 + 4...Nf6 5.O-O: Spanish, Closed and Open (C80-C83 5.O-O Nxe4: Spanish, Open System; C84-C89 5.O-O Be7: Spanish, Closed System)
- C9 C8 + 5...Be7 6.Re1 b5 7.Bb3 d6: Spanish, Closed

D 1.d4 d5; 1.d4 Nf6 2.c4 g6 with 3...d5

- D0 1.d4 d5: Queen's Pawn
- D1 1.d4 d5 2.c4 c6: Slav Defence
- D2 1.d4 d5 2.c4 dxc4: Queen's Gambit Accepted (QGA)
- D3 1.d4 d5 2.c4 e6: Queen's Gambit Declined (QGD)
- D4 D3 + 3.Nc3 Nf6 4.Nf3 c5/c6: Semi-Tarrasch; Semi-Slav
- D5 D3 + 3.Nc3 Nf6 4.Bg5: QGD Classical
- D6 D5 + 4...Be7 5.e3 O-O 6.Nf3 Nbd7: QGD Orthodox
- D7 1.d4 Nf6 2.c4 g6 with 3...d5: Grunfeld
- D8 1.d4 Nf6 2.c4 g6 3.Nc3 d5: Grunfeld
- D9 1.d4 Nf6 2.c4 g6 3.Nc3 d5 4.Nf3: Grunfeld

E 1.d4 Nf6 2.c4 e6; 1.d4 Nf6 2.c4 g6

- E0 1.d4 Nf6 2.c4 e6: Catalan, etc
- E1 1.d4 Nf6 2.c4 e6 3.Nf3 (b6): Queen's Indian, etc
- E2 1.d4 Nf6 2.c4 e6 3.Nc3 (Bb4): Nimzo-Indian, etc
- E3 E2 + 4.Bg5 or 4.Qc2: Nimzo-Indian
- E4 E2 + 4.e3: Nimzo-Indian, Rubinstein
- E5 E4 + 4...O-O 5.Nf3: Nimzo-Indian, main line
- E6 1.d4 Nf6 2.c4 g6: King's Indian
- E7 1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.e4: King's Indian
- E8 E7 + 4...d6 5.f3: King's Indian, Samisch
- E9 E7 + 4...d6 5.Nf3: King's Indian, main lines

(Updated: Scid 2.5, June 2001)