CAIE 0478 & 9618 Variables & Types

2. Variables, Constants & Data Types

Cambridge pseudocode variable declarations, INTEGER, REAL, CHAR, STRING, BOOLEAN, DATE data types, CONSTANT definitions, and arrow (<-) assignments.

All variables must be declared using DECLARE with an explicit data type. Constants use CONSTANT. The assignment operator is <-.

Data Types

Data Type	Description	Literal Examples
`INTEGER`	A whole number	`5`, `-3`
`REAL`	A number with a fractional part	`4.7`, `0.3`, `-4.0`, `0.0`
`CHAR`	A single character	`'x'`, `'C'`, `'@'`
`STRING`	A sequence of zero or more characters	`"Hello"`, `""`
`BOOLEAN`	Logical values	`TRUE`, `FALSE`
`DATE`	A valid calendar date	`dd/mm/yyyy`

Variable & Constant Declarations

PSEUDOCODE Run in Sandbox

// runnable
DECLARE Counter : INTEGER
DECLARE TotalToPay : REAL
DECLARE GameOver : BOOLEAN
DECLARE Initial : CHAR
DECLARE StudentName : STRING

// Comma-separated declarations are also supported per exam mark schemes
DECLARE Low, High, Mid, Target : INTEGER

CONSTANT HourlyRate = 6.50
CONSTANT DefaultText = "N/A"

Assignments

PSEUDOCODE Run in Sandbox

// runnable
// Assignment demo
DECLARE Counter : INTEGER
DECLARE TotalToPay, NumberOfHours : REAL
CONSTANT HourlyRate = 6.50
NumberOfHours <- 4
// The assignment operator is <-
Counter <- 0
Counter <- Counter + 1
TotalToPay <- NumberOfHours * HourlyRate
OUTPUT TotalToPay

Identifier Rules

Can contain letters (A-Z, a-z), digits (0-9), and underscore (_)
Must start with a letter, not a digit
Should be considered case insensitive
Keywords must never be used as variable names
Use descriptive names (e.g. NumberOfPlayers) — single letters are acceptable for loop conventions (e.g. i, j for array indices)