IF ... THEN ... ELSE ... ENDIF (7c)

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Quick Questions

Shade in the A or B circle for each question.

1. Which line is correct pseudocode for the ELSE part of an IF statement?

A ELSE

B ELSE Answer >= 0 THEN

2. When the condition after IF is FALSE, what happens?

A The statements after THEN run

B The statements after ELSE run

3. In an IF ... THEN ... ELSE ... ENDIF statement, how many branches run each time?

A Both, one after the other

B Exactly one

4. Answer is 150. IF Answer < 0 OR Answer > 100 THEN Correct ← FALSE ELSE Correct ← TRUE ENDIF. What is Correct?

A FALSE

B TRUE

5. Answer is 50. IF Answer < 0 OR Answer > 100 THEN Correct ← FALSE ELSE Correct ← TRUE ENDIF. What is Correct?

A TRUE

B FALSE

Match the Pairs

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

Left column		Right column
1IF Mark >= 50 THEN OUTPUT "Pass" ELSE OUTPUT "Fail" ENDIF		AIF Answer < 0 OR Answer > 100 THEN Correct ← FALSE ELSE Correct ← TRUE ENDIF
2ELSE		BIF Age >= 18 THEN OUTPUT "Adult" ELSE OUTPUT "Child" ENDIF
3Check a range: set Correct to FALSE if Answer is outside 0 to 100, otherwise set it to TRUE		CStarts the statements that run when the IF condition is FALSE; it has no condition of its own
4ELSE has no condition, so it is written on its own line with nothing after it		DExactly one message is output: Pass when Mark is 50 or more, otherwise Fail
5IF Score > 10 THEN OUTPUT "High" ELSE Score <= 10 THEN OUTPUT "Low" ENDIF		EThe ENDIF is missing, so the IF ... ELSE structure is never closed. ENDIF must be added after the ELSE branch.
6IF Answer < 0 OR Answer > 100 THEN Correct ← FALSE ELSE Correct ← TRUE		FELSE has been given a condition and THEN. ELSE never has a condition, so it should just be ELSE on its own line.

Definitions

ELSE

Fill in the Blanks

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

Correct ← FALSE ____ Correct ← TRUE

IF Answer < 0 __ Answer > 100 THEN Correct ← FALSE

ELSE Correct ← ____ ENDIF

THEN Correct ← _____ ELSE

ELSE OUTPUT "Well done" _____

Spot the Error

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

Question 1

A IF Answer < 0 OR Answer > 100

B THEN

C Correct = FALSE

D ELSE

E Correct ← TRUE

F ENDIF

Question 2

A INPUT Answer

B IF Answer < 0 AND Answer > 100

C THEN Correct ← FALSE

D ELSE Correct ← TRUE

E ENDIF

Question 3

A IF Mark >= 50

B THEN

C Result ← "Pass"

D ELSE Mark < 50

E Result ← "Fail"

F ENDIF

Question 4

A INPUT Number

B IF Number MOD 2 ← 0

C THEN OUTPUT "Even"

D ELSE OUTPUT "Odd"

E ENDIF

Question 5

A IF Answer < 0 OR > 100

B THEN

C Correct ← FALSE

D ELSE

E Correct ← TRUE

F ENDIF

Answer Key

IF ... THEN ... ELSE ... ENDIF (7c)

Section A: Quick Questions

A — ELSE

B — The statements after ELSE run

B — Exactly one

A — FALSE

A — TRUE

Section B: Match the Pairs

IF Mark >= 50 THEN OUTPUT "Pass" ELSE OUTPUT "Fail" ENDIF → Exactly one message is output: Pass when Mark is 50 or more, otherwise Fail

ELSE → Starts the statements that run when the IF condition is FALSE; it has no condition of its own

Check a range: set Correct to FALSE if Answer is outside 0 to 100, otherwise set it to TRUE → IF Answer < 0 OR Answer > 100 THEN Correct ← FALSE ELSE Correct ← TRUE ENDIF

ELSE has no condition, so it is written on its own line with nothing after it → IF Age >= 18 THEN OUTPUT "Adult" ELSE OUTPUT "Child" ENDIF

IF Score > 10 THEN OUTPUT "High" ELSE Score <= 10 THEN OUTPUT "Low" ENDIF → ELSE has been given a condition and THEN. ELSE never has a condition, so it should just be ELSE on its own line.

IF Answer < 0 OR Answer > 100 THEN Correct ← FALSE ELSE Correct ← TRUE → The ENDIF is missing, so the IF ... ELSE structure is never closed. ENDIF must be added after the ELSE branch.

Section C: Definitions

ELSE — Gives the statements that run when the IF condition is FALSE. ELSE has no condition of its own, so exactly one of the two branches (THEN or ELSE) runs.

Section D: Fill in the Blanks

    Correct ← FALSE
  ELSE
    Correct ← TRUE

IF Answer < 0 OR Answer > 100
  THEN
    Correct ← FALSE

  ELSE
    Correct ← TRUE
ENDIF

  THEN
    Correct ← FALSE
  ELSE

  ELSE
    OUTPUT "Well done"
ENDIF

Section E: Spot the Error

C — Assignment in pseudocode uses the ← arrow. The = sign is used to compare values. It should be Correct ← FALSE.

B — No number is both below 0 and above 100, so AND is always FALSE and the ELSE branch would always run. The condition needs OR.

D — ELSE has no condition. It simply runs when the IF condition is FALSE. The line should be just ELSE.

B — The IF condition compares values, so it needs the comparison operator = and not the assignment arrow ←. It should be IF Number MOD 2 = 0.

A — Each side of OR must be a complete condition. Answer must be repeated: IF Answer < 0 OR Answer > 100.