In base-ten, you don't have a digit for "ten", either: you have "1 ten and 0 ones", for "10". In hexadecimal, which is base-16, you have to use letters, since you run out of digits:
0: 0
1: 1
...
9: 9
10: A
11: B
12: C
13: D
14: E
15: F
16: 10 (being "1 sixteen and 0 ones")
17: 11 (being "1 sixteen and 1 one")
...
25: 19 (being "1 sixteen and 9 ones")
26: 1A (being "1 sixteen and 10 ones")
27: 1B (being "1 sixteen and 11 ones")
...
32: 20 (being "2 sixteens and 0 ones")
...
...and so forth. Whatever base you are using, you don't have a digit for that base. So base-two is 0s and 1s, base-three is 0s, 1s, and 2s, base-four is 0s, 1s, 2s, and 3s, and so forth.
Mark from Neopia wrote:...in base 9, 9 is actually represented by "10"!
There are 10 kinds of people in the world: those who understand binary numbers, and those who don't. :wink:
Eliz.
