Which of the following is NOT a data type?

A variable is a container for storing data values and is not a data type itself. The essence of programming includes understanding that data types define the nature of the data that can be stored and manipulated within a program. For instance, strings, decimals, and integers are all specific data types that dictate how values are treated in computations and operations.

Strings are used to represent text, decimals handle floating-point numbers, and integers are used for whole numbers. In contrast, variables are references to these data types and can hold different data values throughout the execution of a program. Therefore, identifying variables as a separate entity from data types is crucial in programming.