Variables Terminology

Variables are used to store a value that can be changed within the program (as opposed to constants which remain the same throughout the program).

Identifier: the name given to a variable: e.g. score, numberOfLives.

Data Type: A variable has a data type such as:

• Integer
• Real/Float
• Boolean
• String

Declare: Some programming languages require variables to be declared first before they can be used. When declaring a variable you give it an identifier (and a data type for some languages) e.g.

int score

Depending on where in your code you declare a variable will have an impact on its scope.

Scope of a variable: the extent of a program in which the variable is visible/accessible.

A variable which is declared within a subprogram (e.g. procedure or function) is only available within this subprogram. It is a local variable.

A variable which is declared outside any subprograms becomes accessible to code written anywhere in the program. It is a global variable.

Initialise: To give/assign a variable its first value which can be changed later on in the program. e.g.

score = 0

Assign: To give or change the value of a variable, using the assignment operator (=) e.g.
numberOfLives = 3

Casting: to convert/change the data type of a variable

e.g. in Python using functions such as int(), str(), float().

Increment: To increase the value a variable by a value (e.g. 1). e.g.:

score += 1

Decrement: To decrease the value a variable by a value (e.g. 1) e.g.

timer -= 1

List and arrays:

Some more complex data structures such as lists and arrays enable you to store multiple values in a single variable.

e.g.

daysOfTheWeek=[“Monday”,”Tuesday”,“Wednesday”,”Thursday”,”Friday”]

Passing parameters by value or by address/reference: You can pass a variable or its value to a subroutine (function or procedure). This is done either by value (in this case the value of the variable will not change outside the subroutine) or by address/reference (in this case the subroutine may change the value of the variable).