Quick answer
ECO Opening Codes is a notation skill: the legal-move test. Work from the first evidence position for ECO Opening Codes, and begin by testing Kg8.
Begin from Kg8 in 5k2/8/8/8/8/4P3/3K4/8 b - - 0 2. List the fields needed to reconstruct the board and distinguish a position snapshot from a complete game record. The evidence answer is: ECO Opening Codes: identify checks, captures, pins and king safety before accepting a move as legal. Candidate line: Kg8.
In the ECO Opening Codes example, notice: side Black; pieces Black king f8, White pawn e3, White king d2; legal first moves Kg8, Kg7, Kf7, Ke7, Ke8. Treat this piece list as local to the diagram above; it is not a universal map for every similar position.
What the record contains
The first evidence board tests the legal-move test; the second board tests the legal-move test. Replay path A via direct FEN setup; path B is the contrast line direct FEN setup. Look up neighbouring ideas via the Chess Wiki and the Notation And Tools hub. Then compare Notation with Pgn Movetext, Chess Rating Vocabulary, Glicko Versus Elo around the descriptive limit of an ECO code.
The two inventories make the distinction concrete. A contains side Black; pieces Black king f8, White pawn e3, White king d2; legal first moves Kg8, Kg7, Kf7, Ke7, Ke8; B contains side Black; pieces Black king f8, White pawn e3, White king d2; legal first moves Kg8, Kg7, Kf7, Ke7, Ke8. Compare the side to move before comparing the labels in the context of SAN versus long algebraic form.
Topic dossier for this page and board pair r1:5k2 | r2:8 | r3:8 | r4:8 | r5:8 | r6:4P3 | r7:3K4 | r8:8 / r1:5k2 | r2:8 | r3:8 | r4:8 | r5:8 | r6:4P3 | r7:3K4 | r8:8: start with the descriptive limit of an ECO code; then test SAN versus long algebraic form; keep software interoperability separate from castling and en-passant state; use the disambiguation character as the transfer check; and reserve the field boundary in the record for the exception.
Reconstruction test
On the first board, calculate Kg8 after Kg8 and write down the opponent's best reply around the descriptive limit of an ECO code. On the second board, calculate Kg8 after Kg8 and check SAN versus long algebraic form. Use the notation to preserve state, not to infer history that the record does not contain. In this case the useful condition is the field boundary in the record.
Key claim: ECO Opening Codes is illustrated here by the legal-move test; the first concrete test is Kg8. The board anchor is 5k2/8/8/8/8/4P3/3K4/8; the example is intentionally narrower than the topic label and should not be generalised without checking the surrounding position..
Practical boundary: To answer “How can a player read eco opening codes accurately and reconstruct the position or game record it describes?”, compare the recorded setup with Kg8 and the opponent's reply. The decision is useful only when the stated condition survives that concrete test on board 5k2/8/8/8/8/4P3/3K4/8. The evidence records The position tests the stated rule or record field; verify the relevant source when a procedural decision matters and the second board signature r1:5k2 | r2:8 | r3:8 | r4:8 | r5:8 | r6:4P3 | r7:3K4 | r8:8. The false-positive test is whether software interoperability appears without castling and en-passant state, so the conclusion is useful only when the stated condition survives that concrete test.
Evidence positions
example-1: the legal-move test
Show answer
ECO Opening Codes: identify checks, captures, pins and king safety before accepting a move as legal. Candidate line: Kg8.
Why this position is here: ECO Opening Codes is represented by the legal-move test. This is a direct FEN setup with board anchor 5k2/8/8/8/8/4P3/3K4/8; no opening history is inferred from the diagram.
FEN: 5k2/8/8/8/8/4P3/3K4/8 b - - 0 2
Question: What is the first concrete decision in this eco opening codes position?
Answer cue: ECO Opening Codes: identify checks, captures, pins and king safety before accepting a move as legal. Candidate line: Kg8. The first candidate to test is Kg8. Replay Kg8 on board anchor 5k2/8/8/8/8/4P3/3K4/8 and write down what changes after it.
Evidence boundary: The position tests the stated rule or record field; verify the relevant source when a procedural decision matters.
Reading the record
Read the first example (id example-1) as a complete record: continuation Kg8, source fide-laws. This is a direct FEN setup with board anchor 5k2/8/8/8/8/4P3/3K4/8; no opening history is inferred from the diagram. If A does not expose the legal-move test, correct the evidence before relying on the prose.
Read the second example (id example-1) separately: continuation Kg8, source fide-laws. Its feature is the legal-move test; inventory side Black; pieces Black king f8, White pawn e3, White king d2; legal first moves Kg8, Kg7, Kf7, Ke7, Ke8. Compare what changes between Kg8 and Kg8.
Missing information
The main mistake to avoid with ECO Opening Codes is treating a compact notation field as if it encoded history or context that it does not actually contain. In A, the missing condition must be located in r1:5k2 | r2:8 | r3:8 | r4:8 | r5:8 | r6:4P3 | r7:3K4 | r8:8 after Kg8; in B, test it against r1:5k2 | r2:8 | r3:8 | r4:8 | r5:8 | r6:4P3 | r7:3K4 | r8:8 after Kg8.
For ECO Opening Codes, the first board's evidence boundary (after Kg8) is The position tests the stated rule or record field; verify the relevant source when a procedural decision matters. The second board's evidence boundary for ECO Opening Codes is The position tests the stated rule or record field; verify the relevant source when a procedural decision matters. If a trusted source or careful calculation changes the conclusion around the disambiguation character, update both the evidence record and this article.
Practice protocol
decode one record at a time, reconstruct the board, and deliberately test one malformed or incomplete input. Start with A's side to move and r1:5k2 | r2:8 | r3:8 | r4:8 | r5:8 | r6:4P3 | r7:3K4 | r8:8; record two candidates, the reply to Kg8 and the correction. Repeat with B's side to move and r1:5k2 | r2:8 | r3:8 | r4:8 | r5:8 | r6:4P3 | r7:3K4 | r8:8; the changed board tests transfer rather than diagram memory.
After the drill, compare your notes with Pgn Movetext, Chess Rating Vocabulary, Glicko Versus Elo through castling and en-passant state. Keep A's rejected alternative beside B's chosen line Kg8; this shows whether the conclusion survived a new board signature.
Sources and scope
Sources for ECO Opening Codes: Portable Game Notation Specification, 1chess.online editorial scope, FIDE Laws of Chess. Source ids are pgn-specification, original-analysis, fide-laws. Primary evidence hook: fide-laws. Comparisons and practice notes are editorial. Evidence revision: 2026-08-remediation-r2.
Scope note for board pair r1:5k2 | r2:8 | r3:8 | r4:8 | r5:8 | r6:4P3 | r7:3K4 | r8:8 / r1:5k2 | r2:8 | r3:8 | r4:8 | r5:8 | r6:4P3 | r7:3K4 | r8:8: this page does not claim that Kg8 is an engine principal variation, that an exact endgame result is verified when the evidence says it is not, or that a tool output replaces human calculation. The conclusion is limited to the recorded boundary and the exception software interoperability.