Lists Lists are among the simplest of ADTs. Like arrays, they are used for collecting data. That is, lists can be used to store and retreive data. In effect, a list is an linearly-organized collection of information. Every nonempty list has a unique first element.
Every nonempty list has a unique last element.
Every element except the last has a unique successor. Each element except the first has a unique predecessor. Note that this is a data-oriented description of lists. Suprisingly, different computer scientists have very different views of the operations lists might provide and the meanings of those operations. For example, some expect that the elements in the list stay in the same order after different operations.