Is there a way to check if a memory location has been written?

I want my user to be able to store his program settings in the EEPROM and be able to retrieve them next time the pic powers up.
Example, he stores his password and the program will remember it after power is down. Then on bootup program will check the password, etc.

If FF is the default and you want your program to store some variables (which might happen to be FF) in some memory location then later on there's no way of knowing if the FF at the memory location is an actual data that your program stored or the default that has always been there.

That could get problematic.

I guess you can just store numbers from 0 to FE and check for FF to tell you that a particular location hasn't been written too.

Not a nice way to program but might work. Except for, like you said the FF might be programmer dependant and if you use another programmer which defaults to 0s then you're program's logic has to be changed.

There's gotta be a better way... Please help.