← ACARA Digital Technologies Years 9–10

Drawing OR as two decisions sharing one outcome

In a flowchart, OR is two diamonds whose Yes arrows both reach the same action. The second diamond sits on the first's No path. The action is skipped only if both are No.

Part of: ACARA Digital Technologies Years 9–10 — Algorithms with Logical Operators — Module 20

Understanding Drawing OR as two decisions sharing one outcome in ACARA Digital Technologies Years 9–10

What it does: If the first condition is Yes the action already happens, so only the No path needs to check the second condition. The pseudocode IF A OR B THEN matches the two-diamond flowchart where A and B both lead to one shared action. Two Yes arrows reaching the same action means either condition is enough, so the pseudocode uses OR. Move Diamond 2 to the No arrow of Diamond 1. Then a Yes from either diamond reaches 'Award', and OR works correctly.

Common mistakes: The second diamond belongs on the No path of the first diamond. If it sits on the Yes path, both tests must be true, which is AND, not OR. It should read: No -> D2: storm = Yes? The two diamonds with both Yes arrows reaching the same action draw OR. The rule must say OR, not AND. It should be: IF score >= 90 OR att = 100.

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This module's key terms are also in a printable crossword (Modules 492–534) and word search (Modules 459–534).

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Learning

Duo

A flowchart draws IF age < 12 OR age > 65 as two diamonds. Where does the second diamond go?

On the Yes arrow of the first diamondOn the No arrow of the first diamond

Matches

Diamond 1: temp > 35? Yes goes to 'Stay inside'. Diamond 2: rain = 'yes'? Yes goes to a different box 'Take umbrella'.

↓

The two Yes arrows go to different actions. For OR, both Yes arrows must reach the same action box.

Applying

Meanings

Term

IF A OR B THEN

Meaning

In a flowchart, OR is two diamonds whose Yes arrows both reach the same action. The second diamond sits on the first's No path. The action is skipped only if both are No.

Practice

discount ← FALSE

Testing

Gaps

IF age < 12 age > 64 THEN

Check Answer

Spots

2Yes -> Cancel sport

3Yes -> D2: storm = Yes?

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Quick Questions

1. A flowchart draws IF age < 12 OR age > 65 as two diamonds. Where does the second diamond go?

A. On the Yes arrow of the first diamond

B. On the No arrow of the first diamond ✓

With OR, a Yes from the first diamond already succeeds. We only need to check the second condition when the first answer is No.

2. In an OR flowchart with two diamonds, which arrows lead to the same action box?

A. Both Yes arrows ✓

B. Both No arrows

Either condition being true is enough, so both Yes arrows join up and reach the one shared action.

3. When is the action skipped in a flowchart for IF A OR B?

A. When either diamond answers No

B. Only when both diamonds answer No ✓

OR needs just one true condition. The action is skipped only if A is No and B is No.

4. Which flowchart shows AND and which shows OR? Two diamonds in a row, where the second is on the first's Yes path, show:

A. AND ✓

B. OR

For AND, both answers must be Yes, so the second diamond is on the first's Yes path. For OR, it is on the No path.

5. The first diamond asks: Is the day Saturday? It answers Yes. In an OR flowchart, what happens next?

A. Go straight to the action without asking the second diamond ✓

B. Still ask the second diamond before the action

The first Yes already makes the OR condition true, so the second diamond is not needed on that path.

Match the Pairs

Diamond 1: age < 12? Yes goes to 'Child price'. No goes to Diamond 2: age > 65? Yes goes to 'Child price'. → This draws IF age < 12 OR age > 65. Both Yes arrows reach the same action box.

Diamond 1: day = 'Sat'? No goes to Diamond 2: day = 'Sun'? No goes past the action to the next step. → The action is skipped only when both answers are No, because neither condition was true.

The second diamond sits only on the No path of the first diamond, because it is only needed if the first test failed. → Diamond 1 No arrow → Diamond 2

The flowchart for IF A OR B THEN is drawn with two diamonds, and the Yes arrows from both diamonds go to the same action box. → IF A OR B THEN action ENDIF

Diamond 1: temp > 35? Yes goes to 'Stay inside'. Diamond 2: rain = 'yes'? Yes goes to a different box 'Take umbrella'. → The two Yes arrows go to different actions. For OR, both Yes arrows must reach the same action box.

Diamond 1: score > 90? Yes goes to 'Award'. Yes from Diamond 1 also leads to Diamond 2: attendance = 100? Yes goes to 'Award'. → The second diamond is on the Yes path, which is how AND is drawn. For OR, it must be on the No path of the first diamond.

Key Term

IF A OR B THEN

In a flowchart, OR is two diamonds whose Yes arrows both reach the same action. The second diamond sits on the first's No path. The action is skipped only if both are No.

Fill in the Blanks

1. IF age < 12 OR age > 64 THEN OUTPUT "Discount" ENDIF

Hint: Type the logical operator that gives the discount when either condition is true.

2. D1: Is age < 12? Yes -> Discount D1: No -> D2: Is age > 64? D2: Yes -> Discount, No -> Skip

Hint: Type the answer from the second diamond that leads to the same action as the first diamond's Yes.

3. D1: Is score < 0? Yes -> Error D1: No -> D2: Is score > 100? D2: Yes -> Error, No -> Continue

Hint: Type the answer from the first diamond that sends you on to the second diamond.

4. IF temp > 35 OR temp < 5 THEN OUTPUT "Stay inside" ENDIF

Hint: Type the variable name that the second condition must test.

5. D1: Is temp > 35? Yes -> Warn D1: No -> D2: Is temp < 5? D2: Yes -> Warn, No -> End

Hint: Type the action that both Yes arrows must reach.

Spot the Error

Question 1

A D1: temp > 35?

B Yes -> Cancel sport

C Yes -> D2: storm = Yes?

D Yes -> Cancel sport

E No -> Play sport

Line C — The second diamond belongs on the No path of the first diamond. If it sits on the Yes path, both tests must be true, which is AND, not OR. It should read: No -> D2: storm = Yes?

Question 2

A IF score >= 90 AND att = 100

B D1: score >= 90?

C Yes -> Award prize

D No -> D2: att = 100?

E Yes -> Award prize

F No -> No prize

Line A — The two diamonds with both Yes arrows reaching the same action draw OR. The rule must say OR, not AND. It should be: IF score >= 90 OR att = 100

Question 3

A D1: late = Yes?

B Yes -> Send note home

C No -> D2: late = Yes?

D Yes -> Send note home

E No -> Send nothing

Line C — The second diamond must test the second condition (B). Repeating the first test on the No path is pointless, because late is already known to be No. It should be: No -> D2: absent = Yes?

Question 4

A D1: coins >= 5?

B Yes -> Skip snack

C No -> D2: voucher = Yes?

D Yes -> Buy snack

E No -> Skip snack

Line B — In OR, a Yes from the first diamond must reach the same action as a Yes from the second. Sending it to Skip snack means a true condition would skip the action. It should be: Yes -> Buy snack

Question 5

A D1: smoke = Yes?

B Yes -> Sound alarm

C No -> D2: heat > 50?

D Yes -> Stay quiet

E No -> Stay quiet

Line D — The Yes arrow from the second diamond must lead to the same action as the first Yes arrow. If heat > 50 is true, the alarm must sound. It should be: Yes -> Sound alarm

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