Hexadecimal is an alternative way of counting.

We are used to counting in decimal. Or to a base of 10. This means when we get to the ninth number in a series the next highest figure increments the next digital along.

07. 08. 09. 10

The units reset to a 0 value then keep climbing for another 10 places.

Hexadecimal uses a base of 16 instead of 10. This means that the next digit does not increment until 16 digits have past. So after 9 there are six more numbers.

07. 08. 09. 0A. 0B. 0C. 0D. 0E. 0F then 10

While "10" is the tenth number in decimal. "10" is the seventeenth number in hexadecimal.

Why do this? Well, aside from a bunch of programming reasons - one factor is the amount of information you can store. With 2 digits the maximum number of values you can store in decimal is one hundred. (00-99)
In hexadecimal you can store 255. (00-FF)

One area that you may have seen this is when a computer is figuring out what color something should be.

Every color on your screen is made up if a little red, green or blue light. All that a computer needs to know is how much of each to display.

This is done with a six digit hexadecimal based code. The first two digits represent the colour red. The middle two, the green. And the last two is the blue.

So, a code FF0000 would tell a computer to turn the red light on and remove the green and blue.

00FF00 would be green.
0000FF would be blue.

All the colors on a computer screen are a mix of red, green and blue light.

00FFFF - cyan
FF00FF - magenta
FFFF00 - yellow

This is a little game to help you test your recognition of hex color codes.


David Johns