You are probably familiar with the idea that the same number can be written down in different ways - as a tally, as a normal digital, as a roman number, or even as binary. Hexadecimal is a number system that's based on 16s, and it's useful in ICT and computing for representing large numbers (and also because it's easily converted to binary). Hexadecimal appears in most GCSE Computer Science courses, which also require you to convert between denary and hexadecimal.
In a number system based on tens, each column heading (units, tens, hundreds, etc.) is ten times the value of the column heading to its right, and you can use one of ten values (1-9 and 0) in each position. In a number system based on sixteens, each column heading is sixteen times the one to its right, and you can use one of sixteen values in each position.
There aren't sixteen different digits, though, so what comes after 9? Well, hexadecimal uses the digits 0-9, followed by the letters A-F. This means that counting in hexadecimal would give the sequence 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F, 10, 11, 12, etc.
Conversion Table
| Decimal |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
| Hexadecimal |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
A |
B |
C |
D |
E |
F |
Why we need hexadecimal
Which of the following numbers is easier to remember?
If you think B7 is easier to remember, then perhaps you now understand why often binary is represented in hexadecimal format. Also, as technology has become very advanced computers can now represent very long pieces of binary data with shorter hexadecimal ones. B7 is the same value in hex as 1100 0101 is in binary.
Hexadecimal numbers are most commonly used in ICT and computing to represent colours on web-pages, in drawing applications and in programming.