I think most of us have run into the predecessor joke here already:
There are 10 kinds of people: those who understand binary notation, and those who don’t.
I ran across two variants that amused me enough to want to share them:
There are 10 kinds of people: those who understand ternary notation, those who don’t, and those who thought this was going to be the binary joke.
There are 10 kinds of people, 1 group who understand hexadecimal notation, and F the rest.
Along with all this is:
Christmas is Hallowe’en. Proof: 25 DEC = 31 OCT