Using Hexadecimal
Computer Science: OCR A Level, topic 4.1.11
Using Hexadecimal
Hexadecimal is used in HTML to display colour on websites and to form unique MAC addresses for devices connected to a network.
HTML colours
- In HTML, colours are defined by how much red, green and blue (RGB) there is on a scale of 0 to 255.
- 0 to 255 is the range of numbers that can be represented as a single byte.
- This means we use 2 hexadecimal digits to represent each RGB value.
- HTML colour codes start with a hash symbol followed by 3 pairs of hexadecimal numbers like #00FF00.
HTML colours
- We can break down the HTML colour code #00FF00 in the following way:
- The red value is 00, which means we have 0 units of red.
- The green value is FF, so we have 255 units of green.
- The blue value is 00, so we have 0 units of blue.
- The colour code #00FF00 corresponds to a bright green colour.
MAC addresses
- A MAC address is a number that uniquely identifies a networked device.
- A MAC address is made up of 48 bits which are shown as 6 groups of 2 hexadecimal digits:
- NN-NN-NN-DD-DD-DD or NN:NN:NN:DD:DD:DD
- The first 6 hex digits identify the device manufacturer.
- The second 6 hex digits identify the serial number of the device.
Test yourself on Using Hexadecimal
Which of the following gives the manufacturer of a device with MAC address 6A:BB:17:5D:33:8F?