Not to come off as a know-it-all, but I have to make a couple corrections to your post ;)

The vast majority of mags stripe data is not hexidecimal, but simply alpha-numeric. There are up to 3 tracks of information on a standard 1/2" mag stripe, but usually only track one or two is used. By ANSI/ISO spec, track one holds alpha-numeric characters only, track two and three are numeric only. For instance, on your credit card, your name, account number, BIN and some extra authentication data is on track one, and the same information is usually repeated on track 2 (minus the name since it's alpha). Reason for the redundancy? Track 2 starts at the right hand side of the back and reads left, track 1 read the normal left-to-right.

Slot card - 99% of the systems I've seen only have an account number (usually on track 2) and sometimes some type of site code. There are a few that use hex data, but they are few and far between. Most have just a consectutive number (some with an authentication check digit).

Jim is right, it's the system behind it that holds all the personal information - the card is just a means to access it.