The functions of Collection Services allow you to do expected things with collection objects: create them, add values to them, extract values from them, and so on. Because the programming interfaces of CFArray, CFDictionary, CFSet, and CFBag are very much alike in what they do and how they do it, the follow sections include all these types in their discussions. However, the programming interfaces of CFTree objects are sufficiently different that tasks related to these objects are described in the section Creating and Using Tree Structures.