Why loops?

Remember the square you built — move, turn, move, turn, move, turn, move? You probably thought: there must be a better way than writing this out four times.

There is. It's called a loop, and it's one of the most powerful ideas in all of programming.

A loop says: do this again, n times — or do this forever. One instruction replaces a hundred.

Writing four blocks instead of eight is nice. That's not why loops matter.

Loops matter because of change. Suppose you want your square bigger:

• Without a loop, you edit four separate move blocks. Miss one and you get a wonky shape.
• With a loop, you edit one number. Done.

This is the pattern skill from Chapter 3 paying off. Spot the repetition, name the rule, write it once. Anything written once can be changed once.