Variables & Constants (Cambridge International IGCSE Computer Science)

Exam board Cambridge International · IGCSEUpdated 2024-12-03

Spec point — 8.1.1 · 1 Declare and use variables and constants

A variable is an identifier that can change in the lifetime of a program
Identifiers should be:
- In mixed case (Pascal case)
- Only contain letters (A-Z, a-z)
- Only contain digits (0-9)
- Start with a capital letter and not a digit
A variable can be associated a datatype when it is declared
When a variable is declared, memory is allocated based on the data type indicated

Python
`score = int()` # whole number
`cost = float()` # decimal number
`light = bool()` # data can only have one or two values

A constant is an identifier set once in the lifetime of a program
Constants are generally named in all uppercase characters
Constants aid the readability and maintainability
If a constant needs to be changed, it should only need to be altered in one place in the whole program

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Pseudocode

DECLARE :

DECLARE Age : INTEGER

DECLARE Price : REAL

DECLARE GameOver : BOOLEAN

Python

score = int() # whole number

cost = float() # decimal number

light = bool() # data can only have one or two values

Pseudocode

CONSTANT ←

CONSTANT PI ← 3.142

CONSTANT PASSWORD ← "letmein"

CONSTANT HIGHSCORE ← 9999

Python

PI = 3.142

VAT = 0.20

PASSWORD = "letmein"