something like cheat.dat....

how do you make a .dat data that contains AR code???...

 

You mean like these?

http://cheats.gbatemp.net/Temp/

 

yeah...something like that....

 

Or were you trying to make a custom one?

You can edit any part of the cheat databases once you download them.

 

Yeah..I like to make a custom data....but how do you edit the database???

 

Open it up in Notepad.

Make edits and then save it.

 

Or if you want something with a little more features and a nicer GUI, try using R4CCE, which makes it easy to modify Game IDs, (find Game IDs)
http://hp.vector.co.jp/authors/VA013928/soft_en.html

 

Use R4cce to make and add cheats to a .dat cheatdatabase