if-then-else block

Name:

Date:

Class:

Quick Questions

Shade in the A or B circle for each question.

1. Does an IF-THEN-ELSE block let an algorithm choose between two paths?

A True

B False

2. Which keyword introduces the instructions run when the condition is false?

A THEN

B ELSE

3. Which keyword must follow the condition in an IF statement?

A THEN

B DO

4. Should an IF-THEN-ELSE block be closed with END IF?

A No

B Yes

5. Can an IF-THEN-ELSE block be written without an ELSE branch at all?

A Yes, using IF-THEN alone

B No, ELSE is always required

Match the Pairs

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

Left column		Right column
1IF score >= 50 THEN		AEND IF
2ELSE		BIF-THEN-ELSE block
3A keyword that closes an IF-THEN-ELSE block		CThe condition line is missing THEN after the condition
4A structure that runs different instructions depending on a condition		DIntroduces the instructions run when the condition is false
5IF total > 100 DISPLAY "Over" ELSE DISPLAY "OK" ENDIF		EStarts a selection block and introduces the true branch
6IF stock = 0 DISPLAY "Out" ELSE DISPLAY "In" END IF		FThe closing keyword should be written as END IF, not ENDIF

Definitions

IF-THEN-ELSE

Fill in the Blanks

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

IF x > 0 ____

IF x > 0 THEN DISPLAY "Positive" ____

IF p THEN DISPLAY p ______

__ a = b THEN

IF valid THEN DISPLAY "OK" ____

Spot the Error

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

Question 1

A IF age >= 18 THEN

B DISPLAY "Adult"

C ELSE

D DISPLAY "Minor"

E END OF IF

Question 2

A IF total > 100

B DISPLAY "Over budget"

C ELSE

D DISPLAY "Within budget"

E END IF

Question 3

A IF stock = 0 THEN

B DISPLAY "Out of stock"

C OTHERWISE

D DISPLAY "In stock"

E END IF

Question 4

A IF n < 10 THEN

B DISPLAY "Small"

C ELSE

D DISPLAY "Large"

E END

Question 5

A IF x = y THEN

B DISPLAY "Equal"

C ELSE IF

D DISPLAY "Not equal"

E END IF

Answer Key

if-then-else block

Section A: Quick Questions

A — True

B — ELSE

A — THEN

B — Yes

A — Yes, using IF-THEN alone

Section B: Match the Pairs

IF score >= 50 THEN → Starts a selection block and introduces the true branch

ELSE → Introduces the instructions run when the condition is false

A keyword that closes an IF-THEN-ELSE block → END IF

A structure that runs different instructions depending on a condition → IF-THEN-ELSE block

IF total > 100 DISPLAY "Over" ELSE DISPLAY "OK" ENDIF → The closing keyword should be written as END IF, not ENDIF

IF stock = 0 DISPLAY "Out" ELSE DISPLAY "In" END IF → The condition line is missing THEN after the condition

Section C: Definitions

IF-THEN-ELSE — A selection structure that runs one set of instructions if a condition is true, and a different set if it is false

Section D: Fill in the Blanks

IF x > 0 THEN

IF x > 0 THEN
	DISPLAY "Positive"
ELSE

IF p THEN
	DISPLAY p
END IF

IF a = b THEN

IF valid THEN
	DISPLAY "OK"
ELSE

Section E: Spot the Error

E — The block should close with END IF, not END OF IF.

A — The condition line is missing THEN — it should read IF total > 100 THEN.

C — The keyword for the false branch is ELSE, not OTHERWISE.

E — The block must close with END IF, not just END.

C — A simple two-branch block uses ELSE alone, not ELSE IF, unless chaining a further condition.