REPEAT…UNTIL loop (7d)

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Date:

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Quick Questions

Shade in the A or B circle for each question.

1. A REPEAT…UNTIL loop checks its condition at the END of each pass. True or false?

A True

B False

2. Which loop always runs its body at least once?

A WHILE … DO … ENDWHILE

B REPEAT … UNTIL

3. A REPEAT loop stops when the UNTIL condition is…

A FALSE

B TRUE

4. Count ← 10 REPEAT Count ← Count + 1 UNTIL Count > 5 How many times does the loop body run?

A 1 time

B 0 times

5. Which is the correct way to write a loop that asks for a number until the user enters 1 to 10?

A UNTIL Num >= 1 AND Num <= 10

B UNTIL Num < 1 OR Num > 10

Match the Pairs

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

Left column		Right column
1REPEAT INPUT Guess UNTIL Guess = 7		ANum ← 50 REPEAT OUTPUT Num UNTIL Num > 10
2UNTIL Count = 10		BThe UNTIL condition can never become TRUE because Count only goes up, so the loop never stops. It needs a condition such as Count = 10.
3A REPEAT loop always runs its body at least once, because the condition is checked after the body		CWHILE Num < 5 DO Num ← Num + 1 ENDWHILE
4A WHILE loop checks first and may never run, but a REPEAT loop runs once before it checks		DThe stopping condition: the loop ends when Count equals 10 and repeats while it is FALSE
5REPEAT Count ← Count + 1 ENDREPEAT		EREPEAT loops end with UNTIL and a condition, not ENDREPEAT. The loop needs UNTIL Count = 5 or similar.
6REPEAT Count ← Count + 1 UNTIL Count < 0		FAsks for a guess at least once and keeps asking until the guess equals 7

Definitions

REPEAT ... UNTIL condition

Fill in the Blanks

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

REPEAT INPUT Guess _____ Guess = 7

______ Count ← Count + 1 UNTIL Count = 5

REPEAT INPUT Password UNTIL Password _ "open"

REPEAT INPUT Number UNTIL Number >= 1 ___ Number <= 10

REPEAT Lives ← Lives - 1 UNTIL Lives __ 0

Spot the Error

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

Question 1

A Num ← 1

B REPEAT

C Num = Num * 2

D UNTIL Num > 100

E OUTPUT Num

Question 2

A Count ← 0

B REPEAT

C INPUT Mark

D Count ← 1

E UNTIL Mark = -1

F OUTPUT Count

Question 3

A Attempts ← 0

B WHILE Code ≠ 1234 DO

C INPUT Code

D Attempts ← Attempts + 1

E UNTIL Code = 1234

Question 4

A Num ← 10

B REPEAT

C Num ← Num + 2

D UNTIL Num <= 0

E OUTPUT Num

Question 5

A DECLARE Age : INTEGER

B DO

C INPUT Age

D UNTIL Age >= 1 AND Age <= 120

Answer Key

REPEAT…UNTIL loop (7d)

Section A: Quick Questions

A — True

B — REPEAT … UNTIL

B — TRUE

A — 1 time

A — UNTIL Num >= 1 AND Num <= 10

Section B: Match the Pairs

REPEAT INPUT Guess UNTIL Guess = 7 → Asks for a guess at least once and keeps asking until the guess equals 7

UNTIL Count = 10 → The stopping condition: the loop ends when Count equals 10 and repeats while it is FALSE

A REPEAT loop always runs its body at least once, because the condition is checked after the body → Num ← 50 REPEAT OUTPUT Num UNTIL Num > 10

A WHILE loop checks first and may never run, but a REPEAT loop runs once before it checks → WHILE Num < 5 DO Num ← Num + 1 ENDWHILE

REPEAT Count ← Count + 1 ENDREPEAT → REPEAT loops end with UNTIL and a condition, not ENDREPEAT. The loop needs UNTIL Count = 5 or similar.

REPEAT Count ← Count + 1 UNTIL Count < 0 → The UNTIL condition can never become TRUE because Count only goes up, so the loop never stops. It needs a condition such as Count = 10.

Section C: Definitions

REPEAT ... UNTIL condition — A loop that runs its lines first, then checks the UNTIL condition. It stops when the condition is TRUE, so the body always runs at least once.

Section D: Fill in the Blanks

REPEAT
   INPUT Guess
UNTIL Guess = 7

REPEAT
   Count ← Count + 1
UNTIL Count = 5

REPEAT
   INPUT Password
UNTIL Password = "open"

REPEAT
   INPUT Number
UNTIL Number >= 1 AND Number <= 10

REPEAT
   Lives ← Lives - 1
UNTIL Lives <= 0

Section E: Spot the Error

C — In Cambridge pseudocode, values are assigned with ←, not =. The line should be Num ← Num * 2. The = sign is used to compare values.

D — Count is reset to 1 on every pass, so it can never count more than one. The line should be Count ← Count + 1 to add one each time the loop runs.

B — A loop that ends with UNTIL must start with REPEAT. WHILE...DO belongs with ENDWHILE. The line should be just REPEAT.

C — Num goes up, so Num <= 0 never becomes TRUE and the loop never stops. The line should be Num ← Num - 2 so that Num counts down to the stopping condition.

B — DO is not the keyword that starts a post-condition loop. The loop must open with REPEAT to match the UNTIL line that closes it.