Data types: Understand and use the following appropriately:

The idea

This statement introduces the list of data types that follows in section 3.2.1, so you must both understand each type and use it appropriately. Understanding means knowing what kind of value each type holds and how it is represented; using appropriately means selecting the right type for a given value or task. For example, a whole number such as a score suits an integer, a decimal such as a price suits a real or float, a true/false flag suits a Boolean, a single symbol suits a character, and text suits a string. In a multiple-choice question, match the value or scenario to the type whose definition fits, and reject types that would store the value incorrectly or waste memory.

What earns the marks

• Identifies each listed data type and the kind of value it stores, such as integer for whole numbers and Boolean for true/false.
• Selects an appropriate data type for a given value or scenario rather than an unsuitable one.
• Explains why a chosen type is appropriate, referring to the nature of the value and valid operations.
• Recognises that using an inappropriate type can cause errors or incorrect results.

Common mistakes and how to put them right

• Choosing a string for a value that will be used in arithmetic.

  Put it right: Select a numeric type so calculations are valid.

• Treating a character and a string as interchangeable.

  Put it right: A character holds a single symbol while a string holds text of any length.

• Ignoring the purpose of the value and picking any type.

  Put it right: Match the type to how the value will be stored and used.

Exam tips

• Identify what the value represents before selecting a type.
• Reject options that cannot store the value correctly, such as a Boolean for a price.
• If asked why, link the type to the value's nature and the operations needed.