iOS (previously iPhone OS) is a mobile operating system developed by Apple Inc. and distributed exclusively for Apple hardware.
Originally unveiled in 2007 for the iPhone, it has been extended to support other Apple devices such as the iPod Touch (September 2007), iPad (January 2010), iPad Mini (November 2012) and second-generation Apple TV onward (September 2010). As of October 2013, Apple's App Store contained more than 1 million iOS applications, 500,000 of which were optimized for iPad. These apps have collectively been downloaded more than 60 billion times. It had a 21% share of the smartphone mobile operating system units shipped in the fourth quarter of 2012, behind Google's Android. By the middle of 2012, there were 410 million devices activated. According to the special media event held by Apple on September 12, 2012, 400 million devices had been sold by June 2012.
The user
interface of iOS is based on the concept of direct manipulation, using multi-touch
gestures. Interface control elements consist of sliders, switches,
and buttons. Interaction with the OS includes gestures such as swipe, tap,
pinch, and reverse pinch, all of which have specific definitions
within the context of the iOS operating system and its multi-touch interface.
Internal accelerometers are used by some applications to
respond to shaking the device (one common result is the undo command) or
rotating it in three dimensions (one common result is
switching from portrait to landscape mode).
iOS shares with OS X some frameworks such
as Core Foundation and Foundation;
however, its UI toolkit is Cocoa Touch rather than OS X's Cocoa,
so that it provides the UIKit framework rather than the AppKit
framework. It is therefore not compatible with OS X for applications.
Also while iOS also shares the Darwin foundation with OS X, Unix-like
shell access is not available for users and
restricted for apps, making iOS not fully Unix-compatible either.
Major versions of iOS are
released annually. The current release, iOS 7, was
released on September 18, 2013. In iOS, there are four abstraction
layers: the Core OS layer, the Core Services
layer, the Media layer, and the Cocoa Touch layer. The current version of the
operating system (iOS 7.1), dedicates 1–1.5 GB of the device's flash memory for
the system partition, using roughly 800 MB of that partition (varying by model)
for iOS itself.
It runs on the iPhone 4 and later, 2nd-generation iPad and later, all models of
the iPad Mini, and the 5th-generation iPod Touch.
Source :iOS
