ECO chess codes for C4 - Double King Pawn followed by 2. Nf3
C40
1. e4 e5
2. Nf3
C41 - Philidor Defence
1. e4 e5
2. Nf3 d6
C42 - Petroff Defense
1. e4 e5
2. Nf3 Nf6
C43 - Petroff Defense/Steinitz Variation
1. e4 e5
2. Nf3 Nf6
3. d4
C44
1. e4 e5
2. Nf3 Nc6
C45 - Scotch Game
1. e4 e5
2. Nf3 Nc6
3. d4 ed4
4. Nd4
C46 - Three Knights Game
1. e4 e5
2. Nf3 Nc6
3. Nc3
C47 - Scotch Four Knights Game
1. e4 e5
2. Nf3 Nc6
3. Nc3 Nf6
4. d4
C48 - Four Knights Game
1. e4 e5
2. Nf3 Nc6
3. Nc3 Nf6
4. Bb5
C49
1. e4 e5
2. Nf3 Nc6
3. Nc3 Nf6
4. Bb5 Bb4
ECO Chess Codes