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a. What You Need To Know

Key Knowledge - KK 3.1.8

Features of a programming language, including:

  • Local and global variables, and constants
  • Functions and methods
  • Classes and objects

Local and global variables

Key Point

A variable is a named memory location used to store data that may change while a program runs.

Local variables

Local Variable Definition

A local variable:

  • is declared inside a function or method
  • can only be accessed within that function or method
  • exists only while that function or method is executing

Local variables are used to:

  • limit access to data
  • reduce unintended changes
  • make programs easier to debug and maintain

Global variables

Global Variable Definition

A global variable:

  • is declared outside all functions and methods
  • can be accessed by any part of the program
  • exists for the entire duration of program execution

Global variables are useful when:

  • many parts of a program need access to the same data

However, overuse of global variables can:

  • make programs harder to debug
  • increase the risk of accidental data modification

Constants

Key Point

A constant is a named value that cannot be changed once it has been assigned.

Constants are used to:

  • represent fixed values (e.g. tax rates, limits, file paths)
  • improve readability
  • prevent accidental changes
  • make maintenance easier

📌 Exam language tip

Constants improve reliability and maintainability of a program.

Functions and methods

Key Point

Functions and methods are modules of code used to break a program into smaller, manageable parts.

This improves:

  • modularity
  • reuse of code
  • readability

Function (textbook definition)

Function Definition

A function is a module of code that:

  • performs a specific task
  • returns a value to the part of the program that called it

Functions are used when:

  • a result is needed for further processing
  • a calculation must be reused
  • a value must be tested in a condition

Example: Function (pseudocode)

ALGORITHM checkUmbrellaUsage()
BEGIN
    INPUT isRaining
    INPUT hasUmbrella

    IF isRaining = True THEN
        IF hasUmbrella = True THEN
            RETURN useUmbrella()
        ELSE
            RETURN getWet()
        ENDIF
    ENDIF

    RETURN False
END

📌 Why this is a function (exam tooltip)

  • It uses RETURN statements
  • A value is sent back to the calling code
  • The result can be stored or used in a decision

📘 Textbook note

Functions in pseudocode use parentheses after their name (e.g. checkUmbrellaUsage()), even when there are no input parameters.

Method (textbook definition)

Method Definition

A method is a module of code that:

  • performs a task
  • does not return a value

Methods are commonly used to:

  • display output
  • update data
  • carry out procedures

Methods are often associated with:

  • classes
  • objects
  • object-oriented programs

Function vs method (very examinable)

Feature Function Method
Returns a value ✅ Yes ❌ No
Performs a task ✅ Yes ✅ Yes
Used in expressions ✅ Yes ❌ No
Common exam use Calculations Procedures

📌 Examiner focus

If a value must be returned, a function should be used.

If no value is required, a method is appropriate.

Classes and objects

Class

Class Definition

A class is a blueprint used to define:

  • attributes (data)
  • behaviours (methods)

A class describes what an object will have and what it can do, but it is not the object itself.

Object

Object Definition

An object is an instance of a class.

Objects:

  • are created from a class
  • store actual data values
  • use the methods defined by the class

Class vs object (exam language)

Term Meaning
Class Template or blueprint
Object A specific instance created from the class

Example:

  • Student → class
  • student1 → object

These programming language features help developers:

  • organise code logically
  • reduce repetition
  • improve maintainability
  • create scalable solutions

40+ Exam reminders

Remember

  • Local variables have limited scope
  • Global variables have program-wide scope
  • Constants prevent accidental data changes
  • Functions return values
  • Methods do not return values
  • Classes define structure; objects store real data