This is an example of a generator and checker program for license keys. It makes all alphabetic keys (6 groups of 5 letters). What is different about this is I paid attention to some documentation on the technology of how "good" serial keys work.
In order to generate a key, you load the generator and type in some customers private and personal info like their name and the date/time of purchase or something, or a customer ID and their name or what ever. So, it uses this unique information an