Relational & Boolean Operations

Spec & Goals 3 min

AQA Spec 3.2.4 & 3.2.5 · Relational and Boolean operations

By the end of this lesson you can:

1. Use the relational operators = ≠ < > ≤ ≥ to produce a Boolean result.
2. Combine conditions with the Boolean operators AND, OR and NOT.
3. Write and evaluate combined conditions inside an IF statement.

Warm-Up 5 min

Last lesson you used MOD and DIV in calculations. Today the result is not a number but a Boolean — True or False.

Quick starter

Aisyah is 15. For each statement, decide if it is true or false:

• age > 12
• age = 18
• age ≥ 13 AND age ≤ 19

Key Concept — relational and Boolean operators 14 min

A relational operator compares two values and produces a Boolean result — either True or False.

Combining conditions: AND, OR, NOT

A Boolean operator combines or reverses Boolean values to build bigger conditions.

• AND — True only when both sides are True.
• OR — True when at least one side is True.
• NOT — reverses the value: True becomes False, and the reverse.

How the operators evaluate for inputs A and B:

Worked Example — is the age a teenager? 12 min

Problem: input an age and output 'Teenager' if it is between 13 and 19 inclusive. Otherwise output 'Not a teenager'.

A teenager satisfies two conditions at once, so we join them with AND.

AQA pseudo-code

age ← USERINPUT
IF age ≥ 13 AND age ≤ 19 THEN
    OUTPUT 'Teenager'
ELSE
    OUTPUT 'Not a teenager'
ENDIF

We can also write the opposite test with NOT. This outputs a warning when the visitor is not an adult:

age ← USERINPUT
IF NOT (age ≥ 18) THEN
    OUTPUT 'Under 18'
ENDIF

For age = 15, the test age ≥ 18 is False, so NOT (False) is True and the message is shown.

The same algorithm in Python

age = int(input("Enter age: "))
if age >= 13 and age <= 19:
    print("Teenager")
else:
    print("Not a teenager")

if not (age >= 18):
    print("Under 18")

In Python, the operators are and, or, not, with == for equal and != for not equal.

Try It Yourself 12 min

📝 Exam Practice 10 min

Answer the way the examiner expects — the command word and the marks tell you how much to write.

Recap & Key Terms 3 min

Relational operators = ≠ < > ≤ ≥ compare values and give a Boolean. Boolean operators AND, OR and NOT combine those Booleans into bigger conditions — most often inside an IF.

Relational operator

An operator that compares two values and returns a Boolean, such as <, ≥ or ≠.

Boolean operator

An operator that combines or negates Boolean values: AND, OR, NOT.

AND

True only when both conditions are True.

OR

True when at least one condition is True.

NOT

Reverses a Boolean — True becomes False and the reverse.

Homework 1 min

Task (≤ 15 min): Write, in AQA pseudo-code, an algorithm that inputs an age and outputs 'Child fare' when the age is under 5 or 60 and over, otherwise 'Full fare'.

age ← USERINPUT
IF age < 5 OR age ≥ 60 THEN
    OUTPUT 'Child fare'
ELSE
    OUTPUT 'Full fare'
ENDIF