Data Representation

What this lesson covers

Data Representation is a 7-part O Level Computer Science lesson. Each part makes one point and then hands over to the next, so it can be read in a sitting or picked up again at the part you stopped on. It defines the idea in plain words before using it, works through an example step by step, breaks the topic into its parts and compares them, names the mistakes that cost marks in an exam, ends with a recap of what to remember.

How it begins

Computers use binary because their circuits have two reliable states: on and off, high and low voltage, 1 and 0. Binary to denary: write the place values 128, 64, 32, 16, 8, 4, 2, 1 above the bits and add those with a 1 beneath. Denary to binary: work left from 128, writing 1 where the value fits and subtracting, 0 where it does not. Hexadecimal is base 16, using 0–9 then A–F for 10–15.

The 7 parts

1. Why binary, and how to convert
2. Binary addition, overflow and shifts
3. Text, images and sound
4. Compression
5. Where marks go
6. What to remember
7. Watch one worked through