ECO chess codes B0 (idea)

B00 - Nimzowitsch Defence
1. e4 Nc6

B01 - Scandinavian Defense 
1. e4 d5

B02 - Alekhine's defense
1. e4 Nf6

B03 
1. e4 Nf6   
2. e5 Nd5   
3. d4

B04 - Alekhine's Defence Classical Variation
1. e4 Nf6   
2. e5 Nd5   
3. d4 d6   
4. Nf3

B05 
1. e4 Nf6   
2. e5 Nd5   
3. d4 d6   
4. Nf3 Bg4

B06 - Modern Defense 
1. e4 g6

B07 - Pirc Defence 
1. e4 d6   
2. d4 Nf6

B08 - Pirc Defence Classical Variation
1. e4 d6   
2. d4 Nf6   
3. Nc3 g6   
4. Nf3

B09 - Pirc Defence, Austrian Attack
1. e4 d6   
2. d4 Nf6   
3. Nc3 g6   
4. f4