Conditions: questions with true or false answers

Step 1 Warm-up recall

From Module 2: how many patterns can 3 bits hold?

Your answer

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Step 2 Learning goal

By the end of this lesson you can:

• define a condition (Foundation);
• evaluate a comparison (Core);
• write a condition from a rule in words (Core).

Step 3 A familiar example

A door checks your card and answers either “open” or “stay shut”. Behind that single answer is a condition: is this card allowed on this door, true or false?

Step 4 Clear explanation

A condition is a statement about the data that is either true or false. A true or false value is called a Boolean value, named after the mathematician George Boole. Conditions are usually written with a comparison.

The figure shows the flow: take a value, apply a comparison and obtain true or false. With the age 17, the condition age ≥ 18 is false. A method uses that answer to choose its next step. To write a condition from a rule in words, find the quantity (age), the comparison (at least) and the limit (18): “a person must be at least 18” becomes age ≥ 18. The entry on the algorithm explains why each step in a method must be this exact.

Step 5 Worked example (4 marks)

Is the condition score ≥ 50 true or false for the score 49?

1. Identify the comparison: greater than or equal to. (1 mark)
2. Substitute the value: 49 ≥ 50. (1 mark)
3. 49 is less than 50. (1 mark)
4. The condition is false. (1 mark)

Step 6 Learner practice (instant-marked)

Step 7 Recap

• A condition is true or false.
• Compare with >, ≥, <, ≤, = or ≠.
• “At least” means ≥ and “more than” means >.

Step 8 Exit ticket (ungraded)

Write conditions for “under 5” and “65 or over”.

Your answer

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Step 9 Go further (Extension)

Read the entry on the algorithm and note where a decision is needed in a sorting method.