Pseudocode and Flowcharts

CIE pseudocode is its own 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. When a question asks for pseudocode, use the CIE keywords (OUTPUT, not print(...)): the 15-mark scenario schemes ignore minor syntax errors, but they credit the logic, so write it in the CIE style the examiner expects.

Variables and assignment

Variables hold values. In CIE pseudocode the arrow operator ← is the only assignment operator. A single = is not assignment in CIE pseudocode; it means equality (comparison), so do not use it to give a variable a value.

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 OF Day
   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).

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 <counter>.
• 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).