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Revision notes for AQA GCSE Computer Science Relational operations in a programming language. Open the guide for explanations and worked examples. Written against the AQA GCSE Computer Science (8525) specification, so the content matches what's examinable rather than general Computer Science background.

Relational operations in a programming language

What you'll learn

  • What a relational operation is and why it always gives TRUE or FALSE.
  • How to use =, ≠, <, >, <= and >= in algorithms.
  • How comparison symbols differ between AQA pseudocode and real programming languages.
  • How to avoid common mistakes with assignment, equality and boundary values.

The basic idea: comparing two values

Programs often need to ask questions such as:

  • Is the password correct?
  • Is the score at least 50?
  • Has the player run out of lives?
  • Is the temperature below 0?

These are all comparisons. A comparison checks how one value relates to another value.

Definition

Relational operation

A relational operation compares two values and produces a Boolean result: either TRUE or FALSE.

The two values being compared are called operands. The symbol that does the comparing is called a relational operator.

For example, in age >= 13:

  • age is an operand
  • >= is the relational operator
  • 13 is another operand
  • the result is either TRUE or FALSE

Diagram showing age and minimumAge feeding into a relational operation, producing a Boolean result that controls an IF decision

Key Idea

The main takeaway

A relational operation does not usually give a number or a word as its result. It answers a yes/no question, so the result is always TRUE or FALSE.

Example

Evaluating comparisons

Suppose these variables have already been assigned:

score ← 72
passMark ← 50
lives ← 0

Work out the result of each comparison.

  1. For score >= passMark, compare 72 with 50. Since 72 is greater than 50, the comparison is TRUE.

  2. For score = passMark, compare whether 72 is exactly the same as 50. They are different values, so the comparison is FALSE.

  3. For lives <= 0, compare 0 with 0. The operator <= means “less than or equal to”, and 0 is equal to 0, so the comparison is TRUE.

The six relational operators

You need to be familiar with these six comparisons.

MeaningCommon AQA pseudocode symbolCommon programming language symbol
Equal to=== in Python/C#
Not equal to≠!= in Python/C#, <> in VB.NET
Less than<<
Greater than>>
Less than or equal to<= or ≤<=
Greater than or equal to>= or ≥>=

Different languages use different symbols, especially for equal to and not equal to. In AQA pseudocode, assignment uses the left arrow ←, so = can be used for comparison. In Python and C#, = is assignment, so == is used for equality.

Common Mistake

Assignment and equality are not the same

score ← 50 stores 50 in score.
score = 50 checks whether score is equal to 50.
In Python, the equality check would be written as score == 50.

Equal to

Equal to checks whether two values are exactly the same.

For example:

IF password = "computer" THEN
    OUTPUT "Access granted"
ENDIF

This condition is only TRUE if the value stored in password is exactly "computer".

Equality is often used with:

  • passwords or usernames
  • menu choices
  • checking if a total has reached a target
  • checking if a variable has a particular value
Tip

Read equality as a question

Read password = "computer" as: “Is password equal to "computer"?”
That helps you remember it is a test, not an instruction to store a value.

Not equal to

Not equal to checks whether two values are different.

For example:

WHILE guess ≠ secretNumber
    INPUT guess
ENDWHILE

The loop continues while guess is different from secretNumber.

This is useful when you want something to continue until the correct value appears.

Example

Tracing not equal to in a loop

Suppose secretNumber ← 7, and the user enters guesses 3, then 9, then 7.

  1. After the first guess, compare 3 ≠ 7. The values are different, so the condition is TRUE and the loop continues.

  2. After the second guess, compare 9 ≠ 7. The values are still different, so the condition is TRUE and the loop continues again.

  3. After the third guess, compare 7 ≠ 7. The values are not different, so the condition is FALSE and the loop stops.

Less than and greater than

Less than means the value on the left is smaller than the value on the right.

temperature < 0

This is TRUE when temperature is below 0.

Greater than means the value on the left is larger than the value on the right.

score > highScore

This is TRUE when score is bigger than highScore.

Order matters. 5 < 10 is TRUE, but 10 < 5 is FALSE.

Example

Choosing the correct direction

A program should output "Too high" if the user’s guess is greater than the answer.

  1. Identify the two values being compared: guess and answer.

  2. Decide which value must be bigger for the message to appear. The guess must be bigger than the answer.

  3. Put the larger-side variable on the left of the > operator: guess > answer.

So the condition should be:

IF guess > answer THEN
    OUTPUT "Too high"
ENDIF

Less than or equal to, greater than or equal to

The operators <= and >= include the boundary value.

A boundary value is the exact cut-off point where the result changes.

For example, if a pass mark is 50:

  • score > 50 means 51 or more is a pass
  • score >= 50 means 50 or more is a pass

Those are not the same.

Key Idea

Inclusive comparisons

<= means “less than or equal to”.
>= means “greater than or equal to”.
The “or equal to” part means the boundary value is included.

Example

Checking a pass mark boundary

A test is passed if the student scores 50 or more. Decide whether to use > or >=.

  1. The boundary value is 50 because that is the exact cut-off score.

  2. The phrase “50 or more” means a score of exactly 50 should pass.

  3. Use >= because it includes equality: score >= 50.

The condition should be:

IF score >= 50 THEN
    OUTPUT "Pass"
ELSE
    OUTPUT "Fail"
ENDIF
Common Mistake

Using the wrong boundary operator

If the rule says “at least”, “no more than”, “minimum”, or “maximum”, you probably need <= or >=, not just < or >.

Using relational operations in algorithms

Relational operations are most often used as conditions.

Definition

Condition

A condition is an expression that is evaluated as TRUE or FALSE, usually to control selection or iteration.

You will commonly see conditions in:

  • IF statements, where the program chooses between different paths
  • WHILE loops, where the program repeats while a condition is TRUE
  • REPEAT...UNTIL loops, where the program repeats until a condition becomes TRUE

Example using selection:

IF age >= 18 THEN
    OUTPUT "Adult ticket"
ELSE
    OUTPUT "Child ticket"
ENDIF

Example using iteration:

WHILE lives > 0
    OUTPUT "Keep playing"
    lives ← lives - 1
ENDWHILE
Example

Interpreting an algorithm condition

Consider this pseudocode:

points ← 12
target ← 15

IF points < target THEN
    OUTPUT "Keep going"
ELSE
    OUTPUT "Target reached"
ENDIF

  1. Evaluate the condition points < target by substituting the current values: 12 < 15.

  2. Since 12 is smaller than 15, the condition is TRUE.

  3. Follow the THEN branch, so the output is "Keep going".

Comparing text values

You can use equality and inequality with strings, such as checking a password or menu option.

For example:

IF choice = "A" THEN
    OUTPUT "Add record"
ENDIF

In many languages, string comparisons are case-sensitive, meaning "A" and "a" are treated as different values.

Common Mistake

Watch the data type

A number stored as text is not always treated the same as a number stored as an integer or real value. For example, in Python, user input is read as a string unless it is converted.

Exam technique

In the exam

  1. Read the comparison as a full question: “Is the left value greater than or equal to the right value?”

  2. Check boundary words carefully: “at least” usually means >=; “no more than” usually means <=.

  3. Do not mix up assignment and comparison: ← stores a value, while relational operators test values.

Self review

Check yourself

  • What Boolean result does 7 <= 7 produce, and why?
  • Which operator would you use for “the password is not equal to "admin"”?
  • A cinema charges adult prices for ages 16 and above. What condition should test for an adult ticket?

Recap questions

Test yourself with 5 quick questions on this guide. Answer them all correctly to complete it.

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