High Quality Content by WIKIPEDIA articles! Core Foundation (also called CF) is a C application programming interface (API) in Mac OS X iOS, and is a mix of low-level routines and wrapper functions. Apple releases most of it as an open source project called CFLite that can be used to write cross-platform applications for Mac OS X, Linux, and Windows (via Cygwin); a third-party open-source implementation called OpenCFLite also exists. Most Core Foundation routines follow a certain naming convention that deal with opaque objects, for example CFDictionaryRef for functions whose names begin with CFDictionary, and these objects are often reference counted (manually) through CFRetain and CFRelease. Internally, Core Foundation forms the base of the types in the Objective-C runtime as well.