Repeat (10) Loop

Learning Goals 3 min

By the end of this lesson you will be able to:

1. Drag a repeat (10) c-block onto the Script Area and snap a body block inside its mouth.
2. Replace ten identical move (10) steps blocks with one repeat (10) loop.
3. Click the green flag and watch the cat trace a square-shaped path on the Stage.

Warm-Up 7 min

Last lesson (Arc 4/8), you learnt wait (1) seconds — waits pace the cat's moves so you can see each one. Today the cat joins the dance party. Arc 5/8 adds the next move: a block that repeats the blocks inside it.

Quick-fire puzzle

Faiz built this tall stack. He clicked the green flag. How far did the cat move in total?

when flag clicked
move (10) steps
move (10) steps
move (10) steps
move (10) steps
move (10) steps
        

New Concept — the repeat (10) c-block 15 min

Think of repeat (10) as a megaphone for blocks. Whatever blocks you drop inside its mouth, it shouts them out ten times, one after the other. You write the instruction once. The computer runs it ten times.

Blocks reference

The shape of a c-block

A c-block is shaped like the letter C — open on the right with a notch at the top and bottom. The opening is called the mouth. Drop other blocks inside the mouth, and they become the loop's body.

repeat (10)
  move (10) steps
end
        

Two important details:

• The body block is indented two spaces. That tells Scratch the block belongs inside the loop's mouth.
• The c-block always closes with end. You won't see the word "end" in the real editor — it just shows the bottom of the C-shape closing back up. But when we write blocks as text, end tells the renderer where the mouth stops.

Five moves → one loop

Remember Faiz's stack from the Warm-Up? Five copies of the same block. Here's the same idea, written as a loop:

when flag clicked
repeat (5)
  move (10) steps
end
        

Want ten moves instead of five? Change the (5) to (10). Want a hundred? Change it to (100). One small edit replaces ninety-five drag-and-drops.

Why it matters

Loops are everywhere in coding. Anything you'd do "a few times in a row" — flap a bird's wings, drop ten apples from the sky, draw twelve sides of a clock face — uses a loop. repeat (10) is the simplest one. It will be the engine of half your projects from today onwards.

Worked Example — trace a square path 15 min

Open Scratch. Make sure the cat is at the centre (x = 0, y = 0) and facing right (Direction = 90). We'll loop a four-step pattern four times to draw an invisible square — a path of moves and turns.

Step 1 — Start with the hat block

Drag when ⚑ clicked from Events into the Script Area.

Step 2 — Find the orange Control category

In the Blocks Panel, click the orange dot — Control. You'll see wait (1) seconds from last lesson, and just below it the new c-block: repeat (10).

Step 3 — Drag the repeat block

Grab repeat (10). Drag it under the hat block. Snap. The mouth is now waiting for body blocks.

Step 4 — Change the number to 4

Click on the white 10 in the loop. Type 4. Press Enter. Now the loop will run four times.

Step 5 — Drop one move block into the mouth

Grab move (50) steps from Motion. Drag it slowly into the mouth of the loop — the inside of the C. A white highlight appears. Drop it.

Step 6 — Add a turn block under the move (still inside the mouth)

Grab turn cw (15) degrees from Motion. Edit the (15) to 90. Drop it under the move block, still inside the loop's mouth. Both blocks are now the loop's body.

when flag clicked
repeat (4)
  move (50) steps
  turn cw (90) degrees
end
        

Step 7 — Click the green flag

The cat moves 50 steps right, turns 90 degrees, moves 50 steps down, turns 90 degrees, moves 50 steps left, turns, moves 50 steps up. It returns to where it started — having traced a 50 × 50 square.

What changed: instead of writing eight blocks (four moves + four turns), you wrote two blocks inside one loop. Less code. Same square. And if you want a hexagon next week? Change the (4) to (6) and the (90) to (60).

The full assembled stack (your reference)

when flag clicked
repeat (4)
  move (50) steps
  turn cw (90) degrees
end
        

Try It Yourself — three small builds 12 min

when flag clicked
repeat (10)
  move (10) steps
end
          

when flag clicked
repeat (10)
  move (10) steps
  wait (0.2) seconds
  move (-10) steps
  wait (0.2) seconds
end
          

when flag clicked
repeat (3)
  move (80) steps
  turn cw (120) degrees
end
          

Mini-Challenge — countdown then jump 5 min

"Cat says a number, then takes a step — three times"

Combine today's repeat (10) with last lesson's wait (1) seconds and the say [...] for (1) seconds block from earlier. Make the cat count down "3", "2", "1" — and step forward after each number.

It works if:

• You click the green flag once.
• The cat shows the same say-then-move pattern three times.
• You only used one repeat (10) block (not three).

when flag clicked
repeat (3)
  say [Step!] for (1) seconds
  move (40) steps
end
          

Recap 2 min

Today you met your first c-block: repeat (10). It has a mouth that holds a body of blocks, and it runs that body the given number of times. One loop replaces many copies of the same block. You used it to trace a square — and any regular polygon — by mixing moves and turns inside the loop.

Loop

A block that runs other blocks more than once. The body runs over and over until the loop stops.

repeat (10) (block)

A Control c-block that runs the blocks inside its mouth N times, then carries on with the blocks below.

c-block

A block shaped like the letter C, with a mouth that holds a body of other blocks. repeat (10) is your first.

Body (of a loop)

The blocks that sit inside the c-block's mouth. They are the instructions that get repeated.

Homework 1 min

The 36-corner star. Build a loop that makes the cat trace a star-like flower pattern. The cat will turn 10 degrees after each tiny step — 36 times.

1. Open Scratch. Make sure the cat sits at the centre (x = 0, y = 0).
2. Build this stack:

when flag clicked
repeat (36)
  move (20) steps
  turn cw (10) degrees
end
        

Bring back next class:

• A screenshot of your Script Area showing the four-block stack.
• Your written answer to this question: "36 × 10 = 360 degrees. That's a full circle. So why doesn't the cat end up exactly where it started?" (Hint: it does — but the path it walks is not a circle. What shape is it?)

Heads up for next class: SCR-L01-20 introduces the forever loop — the loop that never stops on its own. The red stop button becomes your new best friend.