An assemblage of items that are randomly accessible by integers, the index. Formal Definition: Ignoring size an array may be seen as an abstract data type with the operations new(), set(i, v, A), and get(i, A), where i is a numeric index, v is a value, and A is an array. The operations may be defined with axiomatic semantics as follows.

1. new() returns an array
2. get(i, set(i, v, A)) = v
3. get(i, set(j, v, A)) = get(i, A) if i ≠ j