How to store information?

OS X: How do applications typically store registration information?

• OS X: I bought and installed shareware application X and want to cleanly delete it. I find that just deleting X and it's related preference files does not completely remove app X from my system. I know this because if I try to install it again, it doesn't ask me for registration information. It magically remembers the registration information. Where do OS X applications usually store the registration information?

• Answer:

  Typically the applications store configuration inside the application package itself: right-click or control-click the .app file and choose "Inspect Package Contents" and you will see the app is really a folder containing lots of other files. But this is not a guarantee. It's the standard way to do it, but in theory a program could create an invisible file anywhere it has write access to, which could be anywhere on your hard disk. Since you are being very cagey about what "X" refers to, I can't be more specific. An application might create a secret invisible file to enforce tryout period restrictions or other license restrictions. That way if you try the demo and it expires you can't just turf it and reinstall to use the demo again.