Trumpkin said:
There are 10 kinds of people in the world, those who understand binary and those who don't.
I don't get that maths joke at all

!
And those who don't know how to count. (Really geeky: 0 is a number, thus 0 is actually counted - work with array's some time, position 0 is the 1st position in the array - binary 00000010 is actually the 3rd number 00000000, 00000001, 00000010 etc.).
Still, it's funnier if you don't say there are 1 kinds of people in the world, so we won't hold it against anyone.