iOS

**iOS** (known as iPhone OS prior to June 2010) is a closed-source, proprietary framework for mobile devices that includes an operating system, middleware and key applications (e-mail, browser, media player and the like). It is owned and developed by Apple.

 iOS is derived from Mac OS X, with which it shares the Darwin operating system. As a consequence, the operating system kernel is based on a heavily modified version of BSD Unix. It supports the POSIX/BSD 4.4/C99 API specifications. Some kernel components are available under an open-source license.

On top of the kernel, Apple has developed a rich set of libraries to handle the needs of modern mobile systems: fonts, 2D and 3D graphics, data storage, communication over the web and over cellular networks, and more. The libraries are organized into four abstraction layers: **Core OS**,**Core Services**, **Media**, and **Cocoa Touch**.

Source: Apple.

 The system libraries of iOS are basically a subset of the libraries of Mac OS X. However, because of the nature of the devices supported by iOS, there are some libraries, both public and private, that are specific to iOS.

The programming language for applications is Objective-C, an extension of C used almost exclusively by Apple.