Topic 1 · How a computer stores a photo
What a picture is really made of
Every photo on your phone looks perfectly smooth. It isn't. Zoom in far enough and the smoothness falls apart into a grid of tiny coloured squares called pixels. Click the photo and keep clicking.
A sunset. Looks smooth, doesn't it?
And each square is just a number
Every square stores its colour as a number. The more bits you spend on that number, the more colours it can be. Tap through them.
1-bit
2 colours
4-bit
16 colours
8-bit
256 colours
24-bit
16.7 million
Tap a number of bits to see the difference.
The exam asks it exactly like this
An image is 800 × 600 pixels at a colour depth of 24 bits. How many bits does it take to store? You have everything you need to work it out.
Hint: width × height × colour depth
What just happened
You learned it by doing, not watching.
Nobody handed you a definition to memorise. You clicked, the photo broke into squares, and the idea landed on its own. That is how every lesson here works.
Now picture your child, every topic, exactly like that.
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Lumira Academy · IGCSE 0478 Computer Science