Cambridge IGCSE Pseudocode Rules: The Conventions That Cost Marks

In IGCSE Computer Science 0478, pseudocode is not pseudo-”whatever you like” — Cambridge defines exact conventions, publishes them in the syllabus, and marks against them. Writing Python-flavoured pseudocode in the exam costs marks every single line. This reference collects the rules that decide credit, and the traps that silently eat them.

Declaration and assignment

Declare with a colon, never “AS”:

DECLARE Counter : INTEGER
DECLARE FullName : STRING
CONSTANT PassMark = 50

Assign with the arrow, never ”=”:

Total ← Total + Mark

Conventions around the code: keywords in UPPER CASE (DECLARE, IF, FOR), variable names in PascalCase (Total, MaxMark).

Input and output

INPUT Mark
OUTPUT "Average: ", Average

The two classic cross-language errors: never write PRINT in pseudocode (that’s Python thinking), and never write AS in a declaration (that’s Visual Basic thinking). OUTPUT and INPUT are the only forms.

Every opener needs its closer

Opener	Closer	Notes
IF … THEN	ENDIF	Even with no ELSE; each nested IF needs its own ENDIF
WHILE … DO	ENDWHILE	Condition tested before the loop body
REPEAT	UNTIL <condition>	Condition tested after — loop always runs once
CASE … OF	ENDCASE	Use OTHERWISE for the default path
FOR C ← 1 TO 10	NEXT C	Identifier included — never a bare NEXT

FOR can take a STEP, including negative: FOR C ← 10 TO 1 STEP −1.

Arithmetic that trips people

• Integer division and remainder use DIV and MOD: Total DIV Count, and the even-number test IF Num MOD 2 = 0 THEN …
• Plain / produces a REAL result — if the question wants integer output, DIV is the operator being tested.
• Type matters at declaration: Average : REAL if the value can be fractional.

Patterns worth having in your hand

Validated input (a recurring Paper 2 pattern):

REPEAT
  INPUT Mark
UNTIL Mark >= 0 AND Mark <= 100

Totalling and counting inside a loop, with the running variables declared and initialised before the loop starts — examiners check the initialisation.

Flowcharts: six shapes only

Cambridge specifies the flowchart symbol set — terminator (START/STOP), process, input/output, decision, and the connectors. The exam expects you to read flowcharts (trace them) more often than to draw them from scratch, but the same discipline applies: one shape, one meaning, arrows that show order.

How to drill this properly

1. Write by hand. The arrow ←, the colon, UPPER-CASE keywords — muscle memory matters when the notation is unfamiliar.
2. Convert code you already know. Take a working Python loop and re-express it in Cambridge pseudocode; the translation errors you make are exactly your exam risks.
3. Trace with a variable table. For every algorithm: columns for each variable, one row per iteration. Tracing is itself a question type.
4. Instant-feedback drilling. Notation errors are binary (right or wrong) — the fastest category to drill with immediate correction. Our smart practice system does exactly this, free with classes.

For the full exam map — papers, topics, revision sequence — see the 0478 complete guide. Sample notes live on the IGCSE notes page; message us to arrange a trial lesson.

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