Type B: More interested in theory than practical applications.
Type C: If you majored in CS, and you really don't know why, you're probably Type C. There's nothing to be held against you, necessarily. But most of the people we didn't know why they were in our class, that's them.
That's the short version - XCorvis, if you get a chance sometime, fill in the gaps. I will too, as I find the time.
EDIT: Keep in mind - Mr. Morris is the canonical Type A - I and XCorvis are Type B.