7.2a Pseudocode & Flowcharts — Cambridge IGCSE CS 0478

Cambridge Pseudocode — The Full Reference

Cambridge has its own pseudocode style that is used in exams. You must learn the exact keywords and structures. The key sections are:

Input / Output

INPUT name
OUTPUT "Hello, ", name
OUTPUT score

Assignment

score ← 0
name ← "Alice"
score ← score + 10

Selection — IF

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

Selection — CASE OF

CASE OF grade
    "A": OUTPUT "Excellent"
    "B": OUTPUT "Good"
    OTHERWISE: OUTPUT "Revise"
ENDCASE

Iteration — FOR loop (count-controlled)

FOR counter ← 1 TO 10
    OUTPUT counter
NEXT counter

Iteration — WHILE loop (pre-condition)

WHILE answer <> "quit" DO
    INPUT answer
ENDWHILE

Iteration — REPEAT...UNTIL (post-condition)

REPEAT
    INPUT number
UNTIL number > 0

Key difference between WHILE and REPEAT

	WHILE...DO	REPEAT...UNTIL
Condition checked	Before the loop body runs	After the loop body runs
Minimum runs	0 times (may never run)	At least 1 time
Stops when	Condition becomes FALSE	Condition becomes TRUE

Cambridge Pseudocode — Operators

Operator	Meaning
`←`	Assignment
`=`	Equals (comparison)
`<>`	Not equal to
`<` `>`	Less than / Greater than
`<=` `>=`	Less than or equal / Greater than or equal
`AND` `OR` `NOT`	Logical operators
`MOD`	Modulus (remainder after division)
`DIV`	Integer division (whole number result)
`&`	String concatenation (joining strings)

Flowcharts — Detailed

Flowcharts use standard symbols connected by arrows to show the flow of an algorithm. In the Cambridge exam you may be asked to:

Read a flowchart and describe what it does (trace through it)
Complete a partially drawn flowchart
Convert pseudocode to a flowchart or vice versa

Standard symbols

Symbol	Shape	Use
Terminator	Oval/Rounded rectangle	START and END of the algorithm
Process	Rectangle	Calculations, assignments, actions
Decision	Diamond (two exits: YES/NO)	Conditions — IF statements, loop conditions
Input/Output	Parallelogram (slanted)	INPUT or OUTPUT
Flow line	Arrow	Shows direction of execution

Exam tip: In Paper 2, you will often be asked to write or complete pseudocode. Always use correct Cambridge keywords (THEN, ENDIF, ENDWHILE, NEXT, etc.) and the ← symbol for assignment. Common mistakes: using = for assignment (wrong — use ←); using Python-style indentation only with no keywords; forgetting ENDIF or ENDWHILE.

⚠️ Common Mistakes

Using = for assignment — in Cambridge pseudocode this is ALWAYS ←
Forgetting closing keywords: every IF needs ENDIF, every WHILE needs ENDWHILE, every FOR needs NEXT
WHILE checks condition BEFORE the loop body; REPEAT...UNTIL checks AFTER — confusing these loses marks
Not labelling YES/NO exits on the decision diamond in flowcharts

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Worksheet — Pseudocode & Flowcharts

5 questions · 12 marks

Q1Write pseudocode to input 10 numbers from the user and output their total. [3]

✅ Mark scheme

total ← 0 [1]; FOR counter ← 1 TO 10 — INPUT number — total ← total + number — NEXT counter [1]; OUTPUT total [1]

Q2Explain the difference between a WHILE loop and a REPEAT...UNTIL loop in Cambridge pseudocode. [3]

✅ Mark scheme

WHILE: the condition is checked before the loop body runs, so it may execute 0 times [1]; REPEAT...UNTIL: the condition is checked after the loop body runs, so it always executes at least once [1]; WHILE continues while the condition is TRUE; REPEAT...UNTIL continues until the condition becomes TRUE [1]

Q3Write pseudocode using IF...THEN...ELSE to check if a number is positive, negative, or zero. [3]

✅ Mark scheme

IF number > 0 THEN OUTPUT "Positive" [1]; ELSE IF number < 0 THEN OUTPUT "Negative" [1]; ELSE OUTPUT "Zero" ENDIF ENDIF [1] (accept valid nested IF structure)

Q4State what the MOD operator returns. Give an example. [2]

✅ Mark scheme

MOD returns the remainder after integer division [1]; e.g., 17 MOD 5 = 2 (because 17 ÷ 5 = 3 remainder 2) [1]

Q5Name the flowchart symbol that has two exits and state what they represent. [1]

✅ Mark scheme

The diamond (decision symbol) has two exits: YES (condition is true) and NO (condition is false) [1]

Quiz — Pseudocode & Flowcharts

Q 1 of 8

Score

/ 8

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Term	Definition

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Cambridge Pseudocode — The Full Reference

Input / Output

Assignment

Selection — IF

Selection — CASE OF

Iteration — FOR loop (count-controlled)

Iteration — WHILE loop (pre-condition)

Iteration — REPEAT...UNTIL (post-condition)

Key difference between WHILE and REPEAT

Cambridge Pseudocode — Operators

Flowcharts — Detailed

Standard symbols

Worksheet — Pseudocode & Flowcharts

Mini Test — Pseudocode