Branching with IF ... THEN

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Date:

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Quick Questions

Shade in the A or B circle for each question.

1. Which line correctly starts a branch in pseudocode?

A IF it is raining THEN

B if it is raining then

2. The condition is false. What happens to the action inside IF ... THEN?

A The action is skipped

B The action still runs

3. Which one is set out correctly?

A IF score = 10 THEN play a sound END IF

B IF score = 10 THEN play a sound END IF

4. How do you finish an IF ... THEN branch?

A STOP

B END IF

5. Which part is the condition in this branch? IF door is open THEN walk through END IF

A walk through

B door is open

Match the Pairs

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

Left column		Right column
1IF it is raining THEN		AIF, THEN and END IF must be written in capital letters so they stand out from the rest of the steps.
2END IF		BChecks the condition 'it is raining'. The indented action below runs only if it is true.
3The action is indented so it is clearly part of the IF block and runs only when the condition is true.		CIF door is open THEN walk through END IF say hello
4If the condition is false, the action is skipped and the program carries on after END IF.		DThe action is not indented and there is no END IF to close the block.
5if battery is low then plug in charger end if		EIF score > 10 THEN show "Well done!" END IF
6IF lights are off THEN turn on the lights		FMarks the end of the IF block so the computer knows where the branching stops.

Definitions

IF condition THEN action END IF

Fill in the Blanks

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

__ it is raining THEN take an umbrella END IF

IF it is raining ____ take an umbrella END IF

IF it is dark THEN turn on the lamp ______

IF score _ 10 THEN SHOW "You win" END IF

IF door _ locked THEN use the key END IF

Spot the Error

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

Question 1

A SET score TO 12

B IF score > 10

C SAY "Well done!"

D END IF

Question 2

A IF temp < 15 THEN

B SAY "Wear a jacket"

C END

Question 3

A SET bell TO "rang"

B if bell = "rang" then

C SAY "Time for recess"

D END IF

Question 4

A SET weather TO "hot"

B IF weather = "hot" THEN

C SAY "Wear a hat"

D END THEN

Question 5

A IF door is open

B walk through

C END IF

Answer Key

Branching with IF ... THEN

Section A: Quick Questions

A — IF it is raining THEN

A — The action is skipped

A — IF score = 10 THEN play a sound END IF

B — END IF

B — door is open

Section B: Match the Pairs

IF it is raining THEN → Checks the condition 'it is raining'. The indented action below runs only if it is true.

END IF → Marks the end of the IF block so the computer knows where the branching stops.

The action is indented so it is clearly part of the IF block and runs only when the condition is true. → IF score > 10 THEN show "Well done!" END IF

If the condition is false, the action is skipped and the program carries on after END IF. → IF door is open THEN walk through END IF say hello

if battery is low then plug in charger end if → IF, THEN and END IF must be written in capital letters so they stand out from the rest of the steps.

IF lights are off THEN turn on the lights → The action is not indented and there is no END IF to close the block.

Section C: Definitions

IF condition THEN action END IF — Runs the indented action only when the condition is true. If the condition is false, the action is skipped. Write IF and THEN in capitals, indent the action, and finish with END IF.

Section D: Fill in the Blanks

IF it is raining THEN
  take an umbrella
END IF

IF it is raining THEN
  take an umbrella
END IF

IF it is dark THEN
  turn on the lamp
END IF

IF score > 10 THEN
  SHOW "You win"
END IF

IF door = locked THEN
  use the key
END IF

Section E: Spot the Error

B — The IF line is missing THEN. It should be 'IF score > 10 THEN' so the computer knows the action comes next.

C — An IF block must finish with END IF, not just END. The last line should be 'END IF'.

B — IF and THEN must be written in capitals. The line should be 'IF bell = "rang" THEN'.

D — The block must finish with END IF. THEN belongs at the end of the IF line, so line 4 should be 'END IF'.

A — The IF line is missing THEN. It should be 'IF door is open THEN' so the computer knows the action comes next.