iOS Version History

Apple's iOS did not have an official name until the release of the iPhone software development kit (iPhone SDK) on March 6, 2008. Before then, Apple marketing literature simply stated that their iPhone runs a version of "OS X", a reference to iOS's parent, Mac OS X. When introduced, it was namediPhone OS. It was renamed iOS on June 7, 2010, as iPhone was no longer the only device to run iOS.

On June 29, 2007, Apple released the first version of what became iOS – concurrently with the first iPhone. The final 1.x series release was 1.1.5, released shortly before version 2.0.

July 11, 2008 saw the public release of iPhone OS 2.0, with upgrades through version 2.2.1 made available.

June 17, 2009 was the release date for iPhone OS 3.0. It was updated through (and including) version 3.1.3 (release date February 2, 2010).The first generation iPod Touch and iPhone have iPhone OS 3.1.3 as their newest available version. The iPad was introduced with 3.2, a version made specifically for the iPad.

On June 21, 2010, iOS 4.0 was released to the public and was made available only to the iPod Touch and iPhone. 4.0 was announced to have over 1500 new APIs(application programming interface) for developers, with the highly anticipated multitasking feature. The iPod Touch (2nd generation), and iPhone 3G have iOS 4.2.1 as their latest version available. Nevertheless, many features are not available for the iPhone 3G or iPod touch 2nd generation, such as multitasking and home screen backgrounds. iOS 4.2 is the first version to bring major feature parity to the iPhone and iPad. The release of the CDMA iPhone for Verizon Wireless saw a branching of iOS. The 4.2 version sequence continued for the CDMA phone while 4.3 was released for all other products.

On June 6, 2011, Apple previewed iOS 5, Apple TV 4.4 beta and the iOS SDK 5 beta along with iCloud beta among other products. This update introduced iMessage chat between devices running iOS 5, a new notification system, Newsstand subscriptions, Twitterintegrated into iOS, Reminders app, Enhancements to AirPlay, full integration with iCloud and over 200 new features. iOS 5.0 supports all iPad models, iPhone 3GS, iPhone 4 GSM & CDMA, and the iPod Touch (3rd & 4th generation).

iOS 6 was previewed on June 11, 2012 during WWDC 2012, with release announced for Fall 2012. Following the pattern of previous iOS releases, older devices are no longer supported, specifically the iPod Touch (3rd generation) and the iPad (original). Supported devices on this release include the iPhone 3GS onwards, the iPod Touch (4th generation) onwards, and the iPad 2 onwards.

On September 12, 2012 at San Francisco's Yerba Buena Center for the Arts, amongst other items unveiled, Apple announced three iOS related items; the release of the next generation of iPhone, called iPhone 5, the newly redesigned iPod Touch (5th generation), along with the final release of iOS 6.0.

Data sources and for more details click this link: http://en.wikipedia.org/wiki/IOS_version_history