Encrypting and checking passwords in bigger programs

Here's my problem. I'm currently trying to write a small tax programme and in doing so, I'm also protecting it with a password (i.e. the user needs to input the correct password to be able to use the programme).

Can anybody point out how to do so? I'm trying to add my own password obviously, but tutorials I've read so far merely provide their own passwords and don't teach how to set up your own password.

Salem - Thanks a lot!

Anyway, it's just a 'normal' password so only the person in charge of performing the tasks can access the program. I'm not trying to add one that could be changed later one right now. I figure I'd keep at a leisurely pace first and then build on it later on once I do get everything working.