Pseudocode and Flowcharts

Cambridge IGCSE uses its own pseudocode style. It is not real Python or any other language. The rules are deliberately simple, so any student can read or write it regardless of which language they have learned. Marks are lost if you write things like print(...) with brackets when the question asks for pseudocode.

Variables and assignment

Variables hold values. The CIE arrow operator ← is used for assignment (some specifications also accept = or :=).

total ← 0
count ← count + 1
name ← "Alice"
isFinished ← FALSE

Variables are also declared with a data type using DECLARE:

DECLARE Score : INTEGER
DECLARE Name : STRING
DECLARE IsFinished : BOOLEAN
DECLARE Price : REAL

Input and output

Two clean keywords, with no brackets:

INPUT Age
OUTPUT "Welcome to the site, ", Name

IF-THEN-ELSE selection

A standard two-branch selection:

IF Age >= 18
  THEN
    OUTPUT "Welcome to the site"
  ELSE
    OUTPUT "Sorry, this site is for over-18s only"
ENDIF

Selections can be nested to test more than two cases:

IF Score >= 70 THEN
   Grade ← "A"
ELSE
   IF Score >= 60 THEN
      Grade ← "B"
   ELSE
      Grade ← "C"
   ENDIF
ENDIF

For more than a handful of branches, CASE ... OF ... OTHERWISE ... ENDCASE is cleaner:

CASE Day OF
   1 : OUTPUT "Monday"
   2 : OUTPUT "Tuesday"
   3 : OUTPUT "Wednesday"
   4 : OUTPUT "Thursday"
   5 : OUTPUT "Friday"
   OTHERWISE : OUTPUT "Weekend"
ENDCASE

Loops

Three loop constructs are tested by the syllabus; they are compared in section 5.

FOR i ← 1 TO 10
   OUTPUT i
NEXT i

WHILE NotFinished = TRUE DO
   INPUT Answer
   IF Answer = "stop" THEN
      NotFinished ← FALSE
   ENDIF
ENDWHILE

REPEAT
   INPUT Number
UNTIL Number > 0

Arrays

Arrays hold a list of values of the same type:

DECLARE Scores : ARRAY[1:10] OF INTEGER
Scores[1] ← 75
Scores[2] ← 88
OUTPUT Scores[1]

CIE arrays are usually 1-indexed, with the size given as [1:10]. Some other syntaxes use [10].

Arithmetic operators

Comparison operators

Logical operators

Useful string functions

Procedures and functions

PROCEDURE Greet(Name : STRING)
   OUTPUT "Hello, ", Name
ENDPROCEDURE

CALL Greet("Alice")

FUNCTION Square(Value : INTEGER) RETURNS INTEGER
   RETURN Value * Value
ENDFUNCTION

Result ← Square(5)

These are covered in detail in topic 24 (Procedures and Functions).

A complete example

Example — Write a CIE-pseudocode algorithm that asks a user to enter their age and either welcomes them to the site (18 or over) or shows a polite rejection message.

INPUT Age
IF Age >= 18 THEN
   OUTPUT "Welcome to the site"
ELSE
   OUTPUT "Sorry, this site is for over-18s only"
ENDIF

Common pseudocode pitfalls

• Do not use real-language syntax: avoid print(), input(), range(). Stick to OUTPUT, INPUT, FOR ... NEXT.
• Always close compound statements: IF needs ENDIF; WHILE needs ENDWHILE; FOR needs NEXT.
• Indent inside compound statements to make the structure clear; examiners reward readable layout.
• Use UPPERCASE for keywords to make them stand out (IF, THEN, WHILE, DO, NEXT).
• Use clear variable names that describe what they store (StudentScore, not x).