Which data type is used to store whole numbers, both positive and negative?

The data type used to store whole numbers, both positive and negative, is the integer. Integers are a fundamental data type in many programming languages and are specifically designed to represent whole numbers without any fractional component. This makes them ideal for situations where precise counting or indexing is required, as they can efficiently handle calculations involving whole values.

Integers can take on a wide range of values, allowing for both negative and positive whole numbers, which is essential for various applications in programming, such as counters, indexing arrays, or performing mathematical operations where decimal precision is not necessary. The other data types mentioned serve different purposes: strings are used for textual data, decimals represent numbers with fractional parts, and booleans are used for true/false conditions. Thus, integers are the correct choice when specifically focusing on whole numbers.