IF THEN ELSE

The IF structure

IF condition THEN
    statements when TRUE
ELSE
    statements when FALSE
ENDIF

The ELSE part is optional.

Worked example: positive, negative or zero

INPUT n
IF n > 0 THEN
    OUTPUT "positive"
ELSE
    IF n < 0 THEN
        OUTPUT "negative"
    ELSE
        OUTPUT "zero"
    ENDIF
ENDIF

Common mistakes

• Forgetting ENDIF.
• Using = when you mean to compare. In Cambridge pseudocode both assignment and comparison are written carefully: assignment uses <-, comparison uses =.

Practice tasks

1. 1Output "pass" if a mark is 40 or more.
2. 2Output the largest of three numbers.