Cambridge IGCSE 0478 · Topic 7 · 7.2a

Flowcharts

Standard Symbols · Sequence · Selection · Iteration · Reading Flowcharts

CSZoneCambridge IGCSE Computer Science 0478

Flowchart Symbols

Standard Shapes to Know

Symbol Shape	Name	Purpose
Rounded rectangle / oval	Terminator	Start / Stop
Rectangle	Process	Assignment, calculation
Parallelogram	Input / Output	INPUT or OUTPUT data
Diamond	Decision	YES / NO question — branches flow
Arrow	Flow line	Shows direction of algorithm

Cambridge 0478 exams require you to read and complete flowcharts — know what each symbol means

Sequence, Selection & Iteration in Flowcharts

The Three Constructs

Sequence: steps follow one after another in order — arrows go straight down from box to box

Selection: a diamond decision box with YES and NO branches — different paths taken depending on condition

Iteration (loop): an arrow loops back to an earlier point — condition checked each time to decide whether to repeat

Tracing a Flowchart

How to Trace & Dry Run

A trace table is used to manually step through a flowchart or algorithm, recording the value of each variable at each step. This identifies errors in the logic.

Step through each box in order; record variable values in a table column by column

When you reach a decision diamond, evaluate the condition with current variable values and follow the correct branch

If a loop arrow sends you back, trace round again from that point with updated variable values

Exam Practice

Have a go at this question

Cambridge IGCSE 0478 style

Identify the flowchart symbol used for each of the following: (a) a decision, (b) an input or output operation, (c) showing where the algorithm starts.

3 marks

(a) A diamond (rhombus) shape is used for a decision [1]. (b) A parallelogram is used for input or output [1]. (c) An oval / rounded rectangle (terminator) shows the start (and end) of the algorithm [1].

Key Takeaways

What to Remember

Oval = Start/Stop; Rectangle = Process; Parallelogram = Input/Output; Diamond = Decision

Three constructs: Sequence (straight), Selection (diamond branch), Iteration (looping arrow)

Trace table: step through algorithm manually, recording variable values at each step

Decision diamonds have YES and NO exits — follow the correct branch based on the condition