Collection (abstract Data Type)

Collection (abstract Data Type)

In computer science, a collection or container is a grouping of some variable number of data items (possibly zero) that have some shared significance to the problem being solved and need to be operated upon together in some controlled fashion. Generally, the data items will be of the same type or, in languages supporting inheritance, derived from some common ancestor type. A collection is a concept applicable to abstract data types, and does not prescribe a specific implementation as a concrete data structure, though often there is a conventional choice; see container (type theory) for type theory discussion.

Some different kinds of collections are lists, sets, bags (or multisets), trees and graphs. An enumerated type may be either a list or a set.

A fixed-size table (or array) is usually not considered a collection because it holds a fixed number of items, although tables/arrays commonly play a role in the implementation of collections. Variable-sized arrays are generally considered collections, and fixed-size arrays may likewise considered a collection, albeit with limitations.