2. iOS iOS (originally iPhone OS ) is a mobile operating system created and developed by Apple Inc. and distributed exclusively for Aplle hardware. It is the operating system that presently powers many of the company's mobile devices, including the iPhone, iPad, and iPod touch. In September 2015, it was the most commonly used mobile operating system in Canada, the United States, the United Kingdom, Norway, Sweden, Denmark, Japan, and Australia, and the most commonly used tablet operating system in the world.

3. 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 January 2015, Apple's App Store contained more than 1.4 million iOS applications, 725,000 of which are native for iPads. These mobile apps have collectively been downloaded more than 100 billion times.

4. History In 2005, when Steve Jobs began planning the iPhone, he had a choice to either "shrink the Mac, which would be an epic feat of engineering, or enlarge the iPod". Jobs favored the former approach but pitted the Macintosh and iPod teams, led by Scott Forstall and Tony Fadell, respectively, against each other in an internal competition, with Forstall winning by creating the iPhone OS. The decision enabled the success of the iPhone as a platform for third-party developers: using a well- known desktop operating system as its basis allowed the many third- party Mac developers to write software for the iPhone with minimal retraining. Forstall was also responsible for creating a software developer's kit for programmers to build iPhone apps, as well as an App Store within iTunes

6. Siri  Siri is a personal assistant and knowledge navigator which works as an application on supported devices. The service, directed by the user's spoken commands, can do a variety of different tasks, such as call or text someone, open an app, search the web, lookup sports information, find directions or locations, and answer general knowledge questions (e.g. "How many cups are in a gallon?"). Siri was updated in iOS 7 with a new interface, faster answers, Wikipedia, Twitter, and Bing support and the voice was changed to sound more human. Siri is currently only available on the iPhone 4S and later iPhones, the fifth-generation iPod Touch, all of the models of the iPad Mini, and the third-generation and later iPads.

7. Jailbreaking  Since its initial release, iOS has been subject to a variety of different hacks centered around adding functionality not allowed by Apple. Prior to the 2008 debut of Apple's native iOS App Store, the primary motive for jailbreaking was to bypass Apple's purchase mechanism for installing the App Store's native applications. Apple claimed that it will not release iOS software updates designed specifically to break these tools (other than applications that perform SIM unlocking); however, with each subsequent iOS update, previously un-patched jailbreak exploits are usually patched.  Since the arrival of Apple's native iOS App Store, and—along with it—third-party applications, the general motives for jailbreaking have changed. People jailbreak for many different reasons, including gaining filesystem access, installing custom device themes, and modifying the device SpringBoard. An additional motivation is that it may enable the installation of pirated apps. On some devices, jailbreaking also makes it possible to install alternative operating systems, such as Android and the Linux kernel. Primarily, users jailbreak their devices because of the limitations of iOS. Depending on the method used, the effects of jailbreaking may be permanent or temporary

9. iOS 2

10. iOS 3

11. iOS 4

12. iOS 5

13. iOS 6

14. iOS 7

15. iOS 8

16. iOS 9