They're codes for Action Replay.
press a
go on the pokedex then press a on the Pokemon
To open up your bag in Pokemon Diamond, simply press X and go to Bag in the Menu. Then, press A.
Press X
Solaceon Town, next to the PokeCenter.
you jump and press F9.
press Band select and L
press a
press x
Up,Select,B
go to gamesfaqs.com and type in Pokemon diamond and you will see a FAQ button and press that and your done!
Press x on your game