4.3: Opening Classification

This section explains the Scid features for classifying games by their opening moves, and viewing opening code statistics graphically.

Loading the Scid openings file

You should find that when you start Scid, the openings data is loaded automatically. Scid looks for a file called scid.eco for its openings data. If it can't be found (or you have a replacement openings file with a different name), select Load ECO File... from the Options menu to open a different .eco file.

The ECO code system

Scid classifies chess openings using the ECO system. ECO stands for "Encyclopedia of Chess Openings" and the system has been around since the 1960s. It is widely used in chess literature, compact (just one letter and two digits per code), and suitable for international use. There are 500 opening codes, labelled A00 to E99. In general, opening lines get deeper as the code increases. Most strong players know the scheme well and could tell you instantly that the 20 codes C00-C19 are the French (1.e4 e6) for example, and may even know that C15-C19 are the Winawer variation.

For serious chess study, it pays to know at least what openings the 50 basic classes (A0x, A1x, ..., E9x) represent, and it helps to know the system deeper for openings you study. A very brief summary is given below.

Scid ECO Extensions

There are some obvious problems with the ECO classification which are especially apparent for modern games. Five hundred categories are not really sufficient for distinguishing the many opening variations in common use. If all 500 ECO codes were reached with fairly equal frequency in practice, it might be tolerable. But opening fashion has changed a lot since ECO was devised, and some of the 500 are now rarely reached while others (like B22, the Scilian with 2.c3) account for far more than 1/500th of modern games.

There have been attempts to extend the ECO scheme, but none are standard. Scid has its own extension, which you can choose to use or ignore as you wish. Each of the 500 codes can be subdivided further up to 26 subcodes, A00a, A00b, A00c, ..., A00z for example. Not all 500 basic ECO codes have Scid extensions yet, but many of the most popular ECO codes do.

Classifying games

To allocate an ECO code to each game, open the Classify Games window. You can do this from the Maintenance window, or with ECO-Classify Games from the File / Maintenance menu.

You have two choices to make when classifying games. The first is which games to set the ECO code for. Usually you'll want to do it for all games in the database, but you can choose to classify only games in the filter for example. The second choice is whether to use just the basic ECO codes (A00, A01, etc) or use Scid extended codes (described above). If you are going to export the games to PGN files which will be used by other chess software, it is probably best to stick with the basic codes.

ECO opening classification is reasonably fast, around one million games per minute or more depending on your hardware.

The ECO Browser window

The ECO Browser provides a heirarchical graphical view of the ECO opening code statistics for the current database. It is especially useful for

The ECO Browser works best with a large database of games which have had ECO codes assigned. You can open the browser window from the Windows menu, with the Ctrl+Y shortcut, or by clicking on an ECO code and opening name in the game information area (just below the chessboard).

TODO: INSERT SCREENSHOT HERE When you open the ECO Browser, you'll see something like the window shown here. The browser window has two main panels. The upper panel contains a bar chart, while the lower panel has a list of opening names and their moves.

The browser shows statistics for a particular ECO code prefix. At the top level, it shows the frequency of each major category (A, B, C, D, E) in the ECO system. To go to a deeper level, click the left mouse button on a bar in the bar chart. To go back to a shallower view, press the right mouse button anywhere in the bar chart. If you click on an opening line in the lower panel, its moves will be pasted as the current game and see the resulting position will be shown on the main window chessboard.

The ECO Browser Bar Chart

The bars in the bar chart panel deserve further explanation. Each bar has a height indicating the frequency of games in a particular ECO opening code range. As the example image above shows, "Bxx" openings (that's the Sicilian 1.e4 c5 and other 1.e4 openings except 1.e4 e5 and 1.e4 e6) are the most popular in the tutorial sample database, occurring almost 75 times.

There are three colored portions of each bar: light blue (on the bottom) indicates White wins, dark blue (on the top) indicates Black wins, and mild blue (in the middle) indicates draws. If you're using the ECO Browser with the sample database now, click on the "B" bar to see the statistics for B00 to B99 and you should see that B7 scored well for Black while B9 scored well for White in this collection of games.

Further Reading


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This section last updated: version 3.5 (December 2003)