Using a variable as a counter in a loop

Name:

Date:

Class:

Quick Questions

Shade in the A or B circle for each question.

1. A student wants to count how many times a loop repeats. Which line goes inside the loop?

A counter ← counter + 1

B counter ← 0

2. Where should you set a counter to 0?

A Before the loop starts

B Inside the loop at the end

3. A counter starts at 0. The loop repeats 4 times and adds 1 each time. What is the counter after the loop?

A 5

B 4

4. What does a counter variable do in a loop?

A It keeps track of how many times something has happened

B It makes the loop run faster

5. Which loop stops when the counter reaches 10?

A REPEAT counter TIMES UNTIL 0

B REPEAT UNTIL counter = 10

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1counter ← 0		AAdds 1 to the counter each time the loop repeats, so it counts how many times something happened
2counter ← counter + 1		BSets the counter to 0 before the loop starts so counting begins from zero
3Stop the loop when the counter reaches 5		CREPEAT UNTIL counter = 5
4Start counting from zero before the loop begins		DThe counter is set to 0 inside the loop, so it never goes up and the loop never stops. It should be counter ← counter + 1.
5REPEAT UNTIL counter = 4 counter ← 0		EThe counter was never set to 0 before the loop. Add counter ← 0 before the loop so it starts from a known number.
6REPEAT UNTIL counter = 3 counter ← counter + 1		Fcounter ← 0 REPEAT UNTIL counter = 3 counter ← counter + 1

Definitions

counter ← counter + 1

Fill in the Blanks

Complete each line of code by filling in the missing parts.

counter ← _ REPEAT UNTIL counter = 5 counter ← counter + 1

claps ← 0 REPEAT UNTIL claps = 10 claps ← claps _ 1

counter ← 0 REPEAT UNTIL counter _ 5 counter ← counter + 1

jumps ← 0 REPEAT _____ jumps = 8 jumps ← jumps + 1

counter ← 0 REPEAT UNTIL counter = 5 counter ← counter + _

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A counter ← 0

B REPEAT UNTIL counter = 0

C SAY 'Hello'

D counter ← counter + 1

E END REPEAT

Question 2

A counter ← 0

B REPEAT UNTIL counter = 3

C counter ← counter - 1

D SAY counter

E END REPEAT

Question 3

A counter ← 0

B REPEAT 10 TIMES

C counter ← 1

D END REPEAT

E SAY counter

Question 4

A WHEN green flag clicked

B counter ← 5

C REPEAT 5 TIMES

D counter ← counter + 1

E SAY counter

Question 5

A counter ← 0

B REPEAT UNTIL counter = 4

C SAY 'Jump!'

D counter = counter + 1

E END REPEAT

Answer Key

Using a variable as a counter in a loop

Section A: Quick Questions

A — counter ← counter + 1

A — Before the loop starts

B — 4

A — It keeps track of how many times something has happened

B — REPEAT UNTIL counter = 10

Section B: Match the Pairs

counter ← 0 → Sets the counter to 0 before the loop starts so counting begins from zero

counter ← counter + 1 → Adds 1 to the counter each time the loop repeats, so it counts how many times something happened

Stop the loop when the counter reaches 5 → REPEAT UNTIL counter = 5

Start counting from zero before the loop begins → counter ← 0 REPEAT UNTIL counter = 3 counter ← counter + 1

REPEAT UNTIL counter = 4 counter ← 0 → The counter is set to 0 inside the loop, so it never goes up and the loop never stops. It should be counter ← counter + 1.

REPEAT UNTIL counter = 3 counter ← counter + 1 → The counter was never set to 0 before the loop. Add counter ← 0 before the loop so it starts from a known number.

Section C: Definitions

counter ← counter + 1 — A counter is a variable that goes up by 1 each time a loop repeats, so it counts how many times something happened. Set it to 0 before the loop starts.

Section D: Fill in the Blanks

counter ← 0
REPEAT UNTIL counter = 5
  counter ← counter + 1

claps ← 0
REPEAT UNTIL claps = 10
  claps ← claps + 1

counter ← 0
REPEAT UNTIL counter = 5
  counter ← counter + 1

jumps ← 0
REPEAT UNTIL jumps = 8
  jumps ← jumps + 1

counter ← 0
REPEAT UNTIL counter = 5
  counter ← counter + 1

Section E: Spot the Error

B — The counter starts at 0, so 'counter = 0' is already true and the loop never runs. The loop should stop when the counter reaches the target number, so it should be REPEAT UNTIL counter = 5.

C — Subtracting 1 makes the counter go down (-1, -2, ...), so it never reaches 3 and the loop never stops. A counter goes up by 1 each time, so it should be counter ← counter + 1.

C — Setting the counter to 1 inside the loop wipes out the count every time, so it stays at 1. It should add 1 to the old value: counter ← counter + 1.

B — A counter must be reset to 0 before the loop starts. Starting at 5 would make the final count 10, not 5. It should be counter ← 0.

D — The = sign compares two values; it does not change the variable. The counter never goes up, so the loop never ends. Use the assignment arrow: counter ← counter + 1.