How a computer stores a picture

Ages 9 to 12 Read alone or together · about 30 minutes

Read together

A picture on a screen is a grid of tiny squares called pixels. Each pixel has a colour.

A computer saves the picture as a list of numbers for those colours.

Do it

1. Draw an 8 by 8 grid on squared paper. Colour squares to draw a heart or a cross.
2. Write 1 for a coloured square and 0 for an empty one, row by row.
3. Give your list of numbers to a family member to redraw your picture.
4. Compare their picture with yours.

Talk about it

• What does a 1 mean?
• How could we add colours?

For the grown-up

Digital pictures are numbers. More pixels give finer detail. This is an unplugged activity, so no screen is needed.

Mark as done

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Where this comes from

• K-12 Computer Science Framework Steering Committee, K-12 Computer Science Framework (2016), concept: data representation
• Bell, T., Witten, I. H., and Fellows, M., Computer Science Unplugged (activity: image representation)

Written with AI assistance and checked against the sources listed. Please read it before sharing it with a child.