Range (computer programming)

In computer science, the term range may refer to one of two things:

1. The maximum and minimum values that may be stored in a variable.
2. The upper and lower bounds of an array.

Range of a variable

The range of a variable is given as the difference between the highest and lowest value that that variable can hold. For example, the range of an unsigned 16-bit integer variable is -32,768 to +32,767. In the case of an integer, the variable definition is restricted to whole numbers only, and the range will cover every number within it's range (including the maximum and minimum). However, for other numeric types, such as floating point numbers, the range only expresses the largest and smallest number that may be stored - within the range there will be many numbers that cannot be represented.

Range of an array

When an array is numerically indexed, its range is the upper and lower bound of the array. In most programming languages a warning, or possibly a fatal error (or worse!) will occur if you try to access an array element that is outside the range. In some languages, such as C, arrays have a fixed bottom bound (zero) and will contain data at each position up to the upper bound (so an array with 5 elements will have a range of 0 to 4). In others, such as PHP, an array may have holes where no element is defined, and therefore an array with a range of 0 to 4 will have up to 5 elements (and a minimum of 2).