Apple's mobile operating system for its iPhone, iPod touch, iPad, Apple TV and similar devices. iOS was originally called the iPhone OS but was renamed in 2010 to reflect the operating system’s evolving support for additional Apple devices.
Apple iOS is currently in v6.x release, with iOS 6 having debuted in October 2012 in conjunction with the release of the iPhone 5. Recent versions of iOS have introduced a number of powerful new features to the mobile OS, most notably a built-in instant messaging client (iMessage), built-in support for Apple's iCloud personal cloud storage service and Apple's Siri advanced voice recognition application.
Older devices such as the original iPhone and iPod touch are not supported in the iOS 4, iOS 5 and iOS 6 family of updates, and the iPhone 3G and second-generation iPod Touch cannot be updated past iOS version 4.2.1.
The primary competitors to Apple iOS in the mobile operating system space are Windows Phone 7, Google’s Android OS, and the BlackBerry OS. Apple iOS does have a head start in the apps department, with its App Store already featuring more than 500,000 third-party applications.