Numbers Base Systems

Decimal(10) Binary(2) Ternary(3) Octal(8) Hexadecimal(16)
0 0 0 0 0
1 1 1 1 1
2 10 2 2 2
3 11 10 3 3
4 100 11 4 4
5 101 12 5 5
6 110 20 6 6
7 111 21 7 7
8 1000 22 10 8
9 1001 100 11 9
10 1010 101 12 A
11 1011 102 13 B
12 1100 110 14 C
13 1101 111 15 D
14 1110 112 16 E
15 1111 120 17 F
16 10000 121 20 10
17 10001 122 21 11
18 10010 200 22 12
19 10011 201 23 13
20 10100 202 24 14

Each digit can only count to the value of one less than the base. In hexadecimal, the letters A - F are used to represent the digits 10 - 15, so they would only use one character.