Picture of an Array

An array is an object that is used to store a list of values. It is made out of a contiguous block of memory that is divided into a number of cells. Each cell holds a value, and all the values are of the same type. Sometimes the cells of an array are called slots. In the example array pictured at right, each cell holds an int.

The name of this array is data. The cells are indexed 0 through 9. Each cell can be accessed by using its index. For example, data[0] is the cell which is indexed by zero (which contains the value 23). data[5] is the cell which is indexed by 5 (which contains the value 14).

Facts:

• The cells are numbered sequentially starting at zero.
• If there are N cells in an array, the indexes will be 0 through N-1.

Sometimes the index is called a subscript. The expression data[5] is usually pronounced "data-sub-five" as if it were an expression from mathematics: data5.

The value stored in a cell of an array is sometimes called an element of the array. An array has a fixed number of cells, but the values placed in those cells (the elements) may change over time.