Designing an algorithm that uses logical operators with selection and iteration

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Quick Questions

Shade in the A or B circle for each question.

1. A login allows 3 attempts. Which loop condition keeps asking while the password is wrong AND attempts are left?

A WHILE password <> correct AND attempts < 3 DO

B WHILE password <> correct OR attempts < 3 DO

2. A game ends when lives = 0 OR score = 10. Which WHILE condition keeps the game running?

A WHILE lives > 0 AND score < 10 DO

B WHILE lives > 0 OR score < 10 DO

3. The same game uses REPEAT...UNTIL. Which line stops the loop correctly?

A UNTIL lives = 0 AND score = 10

B UNTIL lives = 0 OR score = 10

4. Tickets cost $8 for children under 13 or adults 65 and over. Which IF is correct?

A IF age < 13 AND age >= 65 THEN

B IF age < 13 OR age >= 65 THEN

5. A login loop should run while the user is NOT logged in and has attempts left. Which is correct?

A WHILE NOT loggedIn AND attempts < 3 DO

B WHILE loggedIn AND attempts < 3 DO

Match the Pairs

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

Left column		Right column
1WHILE attempts < 3 AND NOT loggedIn DO		AIF age < 16 AND day <> "Saturday" THEN price ← 8
2UNTIL lives = 0 OR score = 10		BOR keeps the loop running while attempts are under 3, even after a successful login, or while not logged in, even after 3 failures. It should be AND so both conditions must hold.
3A ticket price decision uses AND so the child price only applies on a weekday when the person is under 16		CAND needs both to be true at once, so the game would not end when only lives = 0 or only score = 10. It should use OR.
4The flowchart and the pseudocode agree when both show the same loop, the same decision and the same AND/OR condition		DThe login loop keeps running only while the user has tries left and has not yet logged in. It stops on either event.
5WHILE attempts < 3 OR NOT loggedIn DO		EThe game loop stops as soon as either the player runs out of lives or reaches a score of 10.
6IF lives = 0 AND score = 10 THEN OUTPUT "Game over"		FREPEAT ... IF lives = 0 OR score = 10 THEN stop

Definitions

WHILE + IF + AND/OR/NOT

Fill in the Blanks

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

attempts ← 0 WHILE attempts < 3 ___ correct = FALSE DO attempts ← attempts + 1

IF age < 13 __ age > 64 THEN price ← 8 ENDIF

REPEAT score ← score + 1 _____ lives = 0 OR score = 10

IF age < 18 AND ___ (day = "Sat") THEN price ← 10 ENDIF

WHILE lives > 0 AND score < 10 DO score ← score + 1 ________

Spot the Error

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

Question 1

A life ← 0

B pts ← 0

C WHILE life > 0 AND pts < 10 DO

D IF hit THEN life ← life - 1

E IF gem THEN pts ← pts + 1

F ENDWHILE

Question 2

A INPUT age, isTue

B price ← 15

C IF age < 13 OR isTue THEN

D price = 8

E ENDIF

F OUTPUT price

Question 3

A n ← 0

B INPUT pw

C WHILE pw <> 1234 OR n < 3 DO

D n ← n + 1

E INPUT pw

F ENDWHILE

Question 4

A INPUT age

B WHILE age < 0 AND age > 120 DO

C OUTPUT 'Try again'

D INPUT age

E ENDWHILE

Question 5

A life ← 3

B pts ← 0

C REPEAT

D IF hit THEN life ← life + 1

E IF gem THEN pts ← pts + 1

F UNTIL life = 0 OR pts = 10

Answer Key

Designing an algorithm that uses logical operators with selection and iteration

Section A: Quick Questions

A — WHILE password <> correct AND attempts < 3 DO

A — WHILE lives > 0 AND score < 10 DO

B — UNTIL lives = 0 OR score = 10

B — IF age < 13 OR age >= 65 THEN

A — WHILE NOT loggedIn AND attempts < 3 DO

Section B: Match the Pairs

WHILE attempts < 3 AND NOT loggedIn DO → The login loop keeps running only while the user has tries left and has not yet logged in. It stops on either event.

UNTIL lives = 0 OR score = 10 → The game loop stops as soon as either the player runs out of lives or reaches a score of 10.

A ticket price decision uses AND so the child price only applies on a weekday when the person is under 16 → IF age < 16 AND day <> "Saturday" THEN price ← 8

The flowchart and the pseudocode agree when both show the same loop, the same decision and the same AND/OR condition → REPEAT ... IF lives = 0 OR score = 10 THEN stop

WHILE attempts < 3 OR NOT loggedIn DO → OR keeps the loop running while attempts are under 3, even after a successful login, or while not logged in, even after 3 failures. It should be AND so both conditions must hold.

IF lives = 0 AND score = 10 THEN OUTPUT "Game over" → AND needs both to be true at once, so the game would not end when only lives = 0 or only score = 10. It should use OR.

Section C: Definitions

WHILE + IF + AND/OR/NOT — A complete design where a loop repeats, IF decisions use AND, OR or NOT, and the flowchart and the pseudocode do the same job, so both versions agree.

Section D: Fill in the Blanks

attempts ← 0
WHILE attempts < 3 AND correct = FALSE DO
  attempts ← attempts + 1

IF age < 13 OR age > 64 THEN
  price ← 8
ENDIF

REPEAT
  score ← score + 1
UNTIL lives = 0 OR score = 10

IF age < 18 AND NOT (day = "Sat") THEN
  price ← 10
ENDIF

WHILE lives > 0 AND score < 10 DO
  score ← score + 1
ENDWHILE

Section E: Spot the Error

A — The game should start with 3 lives. With life ← 0 the condition life > 0 is false straight away, so the WHILE loop never runs. It should be life ← 3.

D — A single = compares two values; it does not store one. To set the discount price the line must use the assignment arrow: price ← 8.

C — The loop must stop when the password is right OR the attempts run out, so it keeps going only while BOTH pw is wrong AND n < 3. With OR, a wrong password keeps the loop running after 3 tries. It should be AND.

B — No number can be below 0 and above 120 at the same time, so AND is always false and invalid ages are never re-asked. An invalid age is too low OR too high, so it should be OR.

D — Being hit should cost a life, so life must go down. Adding 1 means life never reaches 0 and the game cannot end that way. It should be life ← life - 1.