Data types: Boolean

The idea

In AQA 8525 section 3.2.1, 'Boolean' is a data type you must recognise and select. A Boolean holds one of only two values: true or false. It is used where a condition has exactly two possible states, such as whether a switch is on, whether a pupil has passed, or whether a password matches. Contrast it with integer and real, which store numbers, and with character and string, which store text. When a question asks which data type suits a value, look for a yes/no or true/false condition; if the answer can only be true or false, choose Boolean. Do not choose Boolean for a value that could take many values, such as an age or a name.

What earns the marks

• Recognises that a Boolean stores only one of two values: true or false.
• Identifies situations with exactly two states, such as on/off or pass/fail, as suited to Boolean.
• Distinguishes Boolean from numeric types (integer, real) and text types (character, string).
• Rejects Boolean for values that can take many possible values, such as an age or a name.

Common mistakes and how to put them right

• Treating Boolean as a number type.

  Put it right by remembering it stores only true or false.

• Choosing Boolean for a value with many possibilities, such as an age.

  Put it right by reserving Boolean for two-state conditions only.

• Confusing Boolean with string text such as the words 'yes' or 'no'.

  Put it right by noting Boolean stores the logical values true and false.

Exam tips

• Look for a two-state condition (true/false, on/off, pass/fail) before selecting Boolean.
• Eliminate numeric and text options first, then confirm the remaining choice is Boolean.
• Check that the value cannot take more than two states, because that rules Boolean out.