Notepad is not used in OS X (as far as I can tell anyhow). A similar, yet more functional app, is TextEdit. TextEdit will open most types of text files. If you happen to have Panther, then it will even open and edit many MS Word documents.
As fro allocating memory to Application, those days are gone. OS X takes care of memory allocation all by itself. Unless you are running Starcraft in Classic, then you can change memory allocation. Perhaps turning down some detail levels or lower the resolution you are playing at may speed things up? Good luck.
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Edit: changed the cannot / can typo.
Don't you hate it hwen you are thinking one thing but type another?