iPhone Operating System (iOS)

iOS (originally iPhone OS) is a mobile operating system developed and distributed by Apple Inc. Originally released in 2007 for the iPhone and iPod Touch, it has since been extended to support other Apple devices such as the iPad and Apple TV. Unlike Windows CE (Mobile and Phone) and Android, Apple does not license iOS for installation on non-Apple hardware. As of March 6, 2012, Apple's App Store contained more than 550,000 iOS applications, which have collectively been downloaded more than 25 billion times. It had a 16% share of the smartphone operating system units sold in the last quarter of 2010, behind both Google's Android and Nokia's Symbian. In May 2010 in the United States, it accounted for 59% of mobile web data consumption (including use on both the iPod Touch and the iPad).

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. The response to user input is immediate and provides a fluid interface. 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 is derived from OS X, with which it shares the Darwin foundation, and is therefore a Unix operating system.

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 5.1.1) uses roughly 770 megabytes of the device's storage, varying for each model.

Version history

• iOS 4.0.1 included a fix to the reception signal strength indicator(s). It was released on July 15, 2010, the day before Apple hosted a press conference to discuss its response to the widely publicized iPhone antenna issues. Apple also released iOS 3.2.1 for the iPad which tweaked the tablet's Wi-Fi connectivity, video playback, and copy-and-paste for PDF attachments, among other updates.
• iOS 4.1 for the iPhone and iPod touch was released on September 8, 2010; the update fixed some bugs reported by users, improved battery life and added several new features:
  
  Game Center, which allows gamers to play multiplayer games online, upload high scores and unlock achievements (though Apple removed Game Center from the iPhone 3G because of reports of slow performance)
  The ability to toggle spell checking on and off
  HDR photography (iPhone 4 and 4S only)
  Ping, a social music network and discovery tool
• iOS 4.1 also updated carrier settings which (at that time in the United States, AT&T 8.0 only). At the same time, TV show rentals became available on the iTunes US Store.
• iOS 4.2 was never released but instead iOS 4.2.1 was released on November 22, 2010. It added iPad compatibility. Further on iOS 4.2.5 was released as a demo version for the CDMA version of the iPhone 4. This iPhone 4 variant was released for Verizon Wireless customers in the US on February 10, 2011, but pre-ordering was available for qualified Verizon Wireless Customers on February 3. The version released with the phone, 4.2.6, has some slight UI changes specifically for the CDMA version of the phone, including a "Personal Hotspot" switch in the Settings app, a service which has to be activated by the carrier in order for the feature to be usable. This became available for purchase from Verizon as a separate plan, as is currently possible on other smartphones.
• iOS 4.3 was released to the public on March 9, 2011, two days before the iPad 2 was available in the United States. In addition to earlier features, the public release of iOS 4.3 included many new features such as a Nitro JavaScript engine in Safari, making Safari run up to twice as fast according to Apple. iTunes Home Sharing also received a major revision in iOS 4.3; it allows users to connect to their home Wi-Fi networks and stream content from iOS devices to speakers, TVs and other devices, or vice versa. Personal Hotspot for iPhone 4 is a new feature to GSM iPhones (previously released with the Verizon CDMA iPhone) that allows the user to create a Wi-Fi network with an iPhone 4 and provide Internet access for up to five other devices on Verizon Wireless, three on AT&T.[19][20] In addition, the side button on the iPad is now customizable, with users able to use it either as a system sound mute or as a screen rotation lock. iOS 4.3 was not released for CDMA iPhones, which stayed on 4.2.x versions until they were upgraded to iOS 5 with the rest of the iOS line on October 12, 2011.
• iOS 5.0 and its features were announced on June 6 at the WWDC 2011 keynote address. The update was released at 6 pm GMT on October 12, 2011. iOS 5 introduced the iCloud service and the Notification Center, as well as improvements to native apps such as Camera. The operating system also features new applications, such as the "Reminders" app and "Newsstand", a special home screen folder and App Store category that contains newspaper and magazine apps. "iMessage" is an application that allows iPod touch, iPhone, and iPad users to communicate, much like a chat service only used between these devices. The iMessage feature has been integrated into the "Messages" application on the iPhone. The iPod application on the iPhone and iPad has now been split into the Music and Video application, just as it had been on the iPod touch. On the iPhone 4S a virtual assistant named Siri was added. Siri allows users to talk to their iPhone 4S and perform various tasks, send messages, create alerts, and do internet searches. The new OS also features Twitter integration. All devices can now be setup without using a desktop or laptop computer. Almost all system apps were updated with new features or a redesigned interface. It also added updated security and bug fixes. According to Apple, the new OS has over 200 new features.
• iOS 5.0.1 was released in the winter of 2011. This update Included a number of various bug fixes and a security update. The update also fixes battery problems with new devices and errors with the iCloud service. Also included were various other bug fixes and some new methods for developers.
• iOS 5.1 was announced alongside the iPad and Apple TV (3rd generations) during a special press event at the Yerba Buena Center for the Arts in San Francisco on March 7, 2012. Not much of the event was dedicated to the new software release, and it was generally viewed as a minimally incremental release. Later that day, users of iOS devices were able to upgrade to the new operating system. New features include support for Siri in Japanese as well as the ability to delete photos from Photo Stream on an iOS device. The iPad also received a redesigned camera app. The over-the-air 3G download limit from the App Store was increased from 20 MB to 50 MB.
• iOS 5.1.1 was released in the spring of 2012. This update included a number of various bug fixes and a security update.