Logical operators AND, OR and NOT

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Quick Questions

Shade in the A or B circle for each question.

1. Which condition is TRUE when Mark is 50 and the condition is Mark >= 0 AND Mark <= 100?

A TRUE, because both conditions are TRUE

B FALSE, because AND needs only one condition

2. Answer is 150. What does Answer < 0 OR Answer > 100 give?

A TRUE, because Answer > 100 is TRUE

B FALSE, because Answer < 0 is FALSE

3. Which range check correctly rejects marks outside 0 to 100?

A Mark < 0 AND Mark > 100

B Mark < 0 OR Mark > 100

4. GameOver is TRUE. What is the value of NOT GameOver?

A FALSE

B TRUE

5. Which loop condition keeps the game running while the game is not over?

A WHILE GameOver DO

B WHILE NOT GameOver DO

Match the Pairs

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

Left column		Right column
1Mark >= 0 AND Mark <= 100		AReverses the BOOLEAN value: TRUE when GameOver is FALSE, FALSE when GameOver is TRUE
2NOT GameOver		BTRUE only when Mark is at least 0 and also at most 100, so it checks a valid range
3OR is TRUE when at least one condition is TRUE, so it can detect a value outside a range		CAnswer < 0 OR Answer > 100
4Brackets make a complex condition clear by showing which part is worked out first		DAND is the wrong operator. No Mark can be below 0 and above 100 at the same time, so the condition is never TRUE. It should use OR.
5IF Mark < 0 AND Mark > 100 THEN		EOR is the wrong operator for a valid range. Every number is at least 0 or at most 100, so the condition is always TRUE. It should use AND.
6IF Mark >= 0 OR Mark <= 100 THEN		F(Age >= 13 AND Age <= 19) OR Student = TRUE

Definitions

AND OR NOT

Fill in the Blanks

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

IF Mark >= 0 ___ Mark <= 100 THEN OUTPUT "Valid mark" ENDIF

IF Answer < 0 __ Answer > 100 THEN OUTPUT "Out of range" ENDIF

WHILE ___ GameOver DO OUTPUT "Keep playing" ENDWHILE

IF ___ (Mark >= 0 AND Mark <= 100) THEN OUTPUT "Invalid" ENDIF

IF Age >= 18 AND (HasId __ HasPass) THEN OUTPUT "Entry allowed" ENDIF

Spot the Error

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

Question 1

A INPUT Mark

B IF Mark >= 0 OR Mark <= 100

C THEN

D OUTPUT "Valid"

E ENDIF

Question 2

A DECLARE Mark : INTEGER

B DECLARE Ok : BOOLEAN

C INPUT Mark

D Ok ← Mark > 0 AND Mark <= 100

Question 3

A GameOver ← FALSE

B Lives ← 3

C WHILE GameOver DO

D INPUT Lives

E GameOver ← Lives = 0

F ENDWHILE

Question 4

A INPUT Answer

B IF Answer < 0 AND Answer > 100

C THEN

D OUTPUT "Out of range"

E ENDIF

Question 5

A INPUT Rain

B INPUT Cold

C IF NOT Rain AND Cold

D THEN

E OUTPUT "Go out"

F ENDIF

Answer Key

Logical operators AND, OR and NOT

Section A: Quick Questions

A — TRUE, because both conditions are TRUE

A — TRUE, because Answer > 100 is TRUE

B — Mark < 0 OR Mark > 100

A — FALSE

B — WHILE NOT GameOver DO

Section B: Match the Pairs

Mark >= 0 AND Mark <= 100 → TRUE only when Mark is at least 0 and also at most 100, so it checks a valid range

NOT GameOver → Reverses the BOOLEAN value: TRUE when GameOver is FALSE, FALSE when GameOver is TRUE

OR is TRUE when at least one condition is TRUE, so it can detect a value outside a range → Answer < 0 OR Answer > 100

Brackets make a complex condition clear by showing which part is worked out first → (Age >= 13 AND Age <= 19) OR Student = TRUE

IF Mark < 0 AND Mark > 100 THEN → AND is the wrong operator. No Mark can be below 0 and above 100 at the same time, so the condition is never TRUE. It should use OR.

IF Mark >= 0 OR Mark <= 100 THEN → OR is the wrong operator for a valid range. Every number is at least 0 or at most 100, so the condition is always TRUE. It should use AND.

Section C: Definitions

AND OR NOT — AND is TRUE only when both conditions are TRUE. OR is TRUE when at least one is TRUE. NOT reverses a BOOLEAN value. Use brackets to make complex conditions clear.

Section D: Fill in the Blanks

IF Mark >= 0 AND Mark <= 100 THEN
    OUTPUT "Valid mark"
ENDIF

IF Answer < 0 OR Answer > 100 THEN
    OUTPUT "Out of range"
ENDIF

WHILE NOT GameOver DO
    OUTPUT "Keep playing"
ENDWHILE

IF NOT (Mark >= 0 AND Mark <= 100) THEN
    OUTPUT "Invalid"
ENDIF

IF Age >= 18 AND (HasId OR HasPass) THEN
    OUTPUT "Entry allowed"
ENDIF

Section E: Spot the Error

B — OR is TRUE when at least one condition is TRUE, so every number passes (for example 150 is >= 0). A range check needs AND so that both conditions must be TRUE: IF Mark >= 0 AND Mark <= 100.

D — Mark > 0 leaves out 0, which is a valid mark. The first part must be Mark >= 0 so that both 0 and 100 are accepted: Ok ← Mark >= 0 AND Mark <= 100.

C — GameOver starts as FALSE, so WHILE GameOver is FALSE straight away and the loop never runs. NOT reverses the value so the loop runs while the game is not over: WHILE NOT GameOver DO.

B — No number can be less than 0 and more than 100 at the same time, so AND is never TRUE. To catch a value outside the range you need OR: IF Answer < 0 OR Answer > 100.

C — Without brackets, NOT only reverses Rain, not the whole condition. The brackets make NOT apply to (Rain AND Cold): IF NOT (Rain AND Cold).