Pseudocode & Flowcharts (Years 6–9) — Computer Science

Planning algorithms with plain-English pseudocode and with standard flowchart shapes.

Two chefs, one recipe. One writes it in French, the other in English — yet both cook the same dish, because the steps are the same. When a programmer plans a solution they want that same freedom: to describe the steps clearly without getting tangled in the fussy grammar of Python or Java. Two tools give them exactly that: pseudocode (the plan written in plain, structured English) and flowcharts (the plan drawn as boxes and arrows).

Why this matters: A plan you can read is a plan you can check for mistakes before you write code. Pseudocode and flowcharts are board-agnostic, so an examiner in any language can follow them — and so can a teammate who has never met you.

A flowchart: oval terminators, a rectangle for a process, a diamond for a decision.

The four flowchart shapes

The four building blocks every flowchart is made from.

Oval (terminator) — START or STOP. Every flowchart begins and ends with one.
Parallelogram — input or output (reading data in, or printing it out).
Rectangle — a process: a calculation or an action.
Diamond — a decision: a yes/no question with two arrows leaving it.

Think of it like a board game: you follow the arrows one square at a time, and the diamond is the "roll again or move on?" junction.

Writing pseudocode

The same choice, two ways: IF...ELSE in text, a diamond in a flowchart.

Many exam boards, including Cambridge IGCSE, use a standard set of pseudocode conventions — a good habit to learn even if you're not sitting that specific exam. Keywords are in CAPITALS, you indent inside a block, assignment uses a left arrow ←, and you declare each variable with a type. The core keywords: DECLARE name : TYPE (INTEGER, REAL, CHAR, STRING, BOOLEAN), INPUT, OUTPUT, IF … THEN … ELSE … ENDIF, CASE OF … OTHERWISE … ENDCASE, WHILE … DO … ENDWHILE, REPEAT … UNTIL and FOR … TO … NEXT. Arrays are 1-based: ARRAY[1:n].

DECLARE age : INTEGER
age ← INPUT("Enter your age")
IF age >= 18 THEN
    OUTPUT "Access allowed"
ELSE
    OUTPUT "Access denied"
ENDIF

Two views of one idea

	Pseudocode	Flowchart
Form	Structured text	Shapes and arrows
Best for	Long or detailed logic	Seeing the overall flow at a glance
Decision shown as	IF … ELSE	A diamond with Yes/No

Worked reasoning: Trace the pseudocode above with age = 15.

With age = 15 the test is False, so the No path runs.

The condition 15 >= 18 is False, so the ELSE branch runs and the program outputs "Access denied". With age = 20, the condition is True, so it outputs "Access allowed".

Common mistake: Using a rectangle for a decision. A yes/no question must be a diamond — and a diamond must always have two arrows leaving it, one for each answer. A rectangle only ever has one arrow out.

Memory hook: Ovals top and tail, Diamonds decide, Rectangles do the work — "Only Dogs Run".