Break the Picture into Parts

💡 The idea

Decomposition: split a problem you cannot solve into parts you can.

• Decomposition means splitting a problem into smaller, independent parts.
• A part is the right size when you can test it on its own in a few seconds.
• Naming a part is real work: the name is the interface everyone reads.
• Solve the parts in any order you like, then compose them at the end.
• The same habit works for essays, experiments and school projects, not just code.

📘 Words to know

decomposition

splitting a problem into smaller parts

abstraction

hiding the details behind a name

compose

join the finished parts into the whole

👀 Watch this

One part of a robot, written as a block called body. Nothing else exists yet, and that is the point.

# step one: name one part and nothing else
to body
square 60
end
body

▶ Run it below

✍️ Your turn

1. Run it, and notice how little it does. That is a healthy first version.
2. On paper, list every part your robot needs: body, head, arms, legs.
3. Write a second block for the head and test it on its own.
4. Decide the join: where does the head sit relative to the body?
5. Call the two blocks one after the other and check the join is right.

🎯 Challenge: Split a flower into two parts, stem and bloom, write a block for each, then draw the whole flower by calling them in order.

to stem
colour green
width 5
forward 110
end
to bloom
colour pink
repeat 6 [ forward 24 dot 20 back 24 right 60 ]
end
stem
bloom