Data types: integer

The idea

An integer is a whole number with no fractional or decimal part, and it may be positive, negative or zero. Examples include 7, -42 and 0, while 3.5 and 0.25 are not integers because they have a fractional part. In programming, an integer data type stores whole-number values, and it is one of the general data types named in section 3.2.1. When answering a multiple-choice question, check whether the value has any decimal or fractional component: if it does not, it is a whole number and so an integer. Remember that negative whole numbers such as -8 are still integers, and zero is an integer too. Distinguish integers from real numbers, which can hold fractional values, and from strings, which hold text.

What earns the marks

• An integer is a whole number with no fractional or decimal part.
• Integers can be positive, negative or zero, for example 7, -42 and 0.
• A value such as 3.5 is not an integer because it has a fractional part; it is a real number.
• The integer data type stores whole-number values and is one of the general data types in section 3.2.1.

Common mistakes and how to put them right

• Believing integers must be positive.

  Put it right: Negative whole numbers such as -42 are also integers.

• Classifying a decimal such as 3.5 as an integer.

  Put it right: A value with a fractional part is a real number, not an integer.

• Forgetting that zero is an integer.

  Put it right: 0 is a whole number and therefore an integer.

Exam tips

• Check for a decimal point or fractional part first: no fraction means the value is a whole number and so an integer.
• Remember that both negative whole numbers and zero count as integers when selecting an option.
• Eliminate options that describe text or fractional values before choosing the whole-number answer.