IOS

iOS (formerly iPhone OS) is Apple's mobile operating system. Originally developed for the iPhone, it has since been extended to support other Apple, Inc. devices such as the iPod Touch, iPad, and Apple TV. Apple, Inc. does not license iOS for installation on third-party hardware. Apple, Inc.'s App Store contains more than 650,000 iOS applications,which have collectively been downloaded more than 18 billion times. It had a 26% 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 USA, 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 multitouch 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 Mac OS X, with which it shares the Darwin foundation, and is therefore a Unix-like operating system by nature. 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 under 50 megabytes of the device's storage, varying for each model

History
The operating system was unveiled with the iPhone at the Macworld Conference & Expo on January 9, 2007, and released in June of that year. At first, Apple marketing literature did not specify a separate name for the operating system, stating simply that the "iPhone runs OS X". Initially, third-party applications were not supported. Steve Jobs argued that developers could build web applications that "would behave like native apps on the iPhone". On October 17, 2007, Apple announced that a Software Development Kit (SDK) was under development and that they planned to put it "in developers' hands in February".On March 6, 2008, Apple released the first beta, along with a new name for the operating system: "iPhone OS". The previous September, Apple had released the iPod touch, which had most of the non-phone capabilities of the iPhone. Many people have also called the iPod touch "an iPhone without the phone". Apple also sold more than one million iPhones during the 2007 holiday season. On January 27, 2010, Apple announced the iPad, featuring a larger screen than the iPhone and iPod touch, and designed for web browsing, media consumption, and reading iBooks. In June 2010, Apple rebranded iPhone OS as "iOS". The trademark "IOS" had been used by Cisco for over a decade for its operating system, IOS, used on its routers. To avoid any potential lawsuit, Apple licensed the "IOS" trademark from Cisco.

Version History
The operating system was unveiled with the iPhone at the Macworld Conference & Expo on January 9, 2007, and released in June of that year. At first, Apple marketing literature did not specify a separate name for the operating system, stating simply that the "iPhone runs OS X".Initially, third-party applications were not supported. Steve Jobs argued that developers could build web applications that "would behave like native apps on the iPhone". On October 17, 2007, Apple announced that a native Software Development Kit (SDK) was under development and that they planned to put it "in developers' hands in February". On March 6, 2008, Apple released the first beta, along with a new name for the operating system: "iPhone OS". The previous September, Apple had released the iPod touch, which had most of the non-phone capabilities of the iPhone. Apple also sold more than one million iPhones during the 2007 holiday season. On January 27, 2010, Apple announced the iPad, featuring a larger screen than the iPhone and iPod touch, and designed for web browsing, media consumption, and reading iBooks. In June 2010, Apple rebranded iPhone OS as "iOS". The trademark "IOS" had been used by Cisco for over a decade for its operating system, IOS, used on its routers. To avoid any potential lawsuit, Apple licensed the "IOS" trademark from Cisco.

Homescreen
The home screen (rendered by "SpringBoard") displays application icons and a dock at the bottom of the screen where users can pin their most frequently used apps. The home screen appears whenever the user switches on the device or presses the "Home" button (a physical button on the device). The screen has a status bar across the top to display data, such as time, battery level, and signal strength. The rest of the screen is devoted to the current application.

Folders
With iOS 4 and for ipod touch 4.2.1 came the introduction of a simple folder system. When applications are in "jiggle mode", any two can be dragged on top of each other to create a folder, and from then on, more apps can be added to the folder using the same procedure, up to 12 on iPhone and iPod touch and 20 on iPad. A title for the folder is automatically selected by the type of applications inside, but the name can also be edited by the user.

Nofification Center
In the iOS 5 update, the notifications feature has been completely redesigned. Notifications now collate in a window which can be dragged down from the top of the screen. And if you touch a received notification, you go to the application that sent the notification.

Multitasking
Before iOS 4, multitasking was limited to a selection of the applications Apple included on the devices. Starting with iOS 4, on 3rd-generation and newer iOS devices, multitasking is supported through seven background APIs: Background audio - application continues to run in the background as long as it is playing audio or video content Voice over IP - application is suspended when a phone call is not in progress Background location - application is notified of location changes Push notifications Local notifications - application schedules local notifications to be delivered at a predetermined time Task completion - application asks the system for extra time to complete a given task Fast app switching - application does not execute any code and may be removed from memory at any time

Game Center
Game Center is an online multiplayer "social gaming network"released by Apple. It allows users to "invite friends to play a game, start a multiplayer game through matchmaking, track their achievements, and compare their high scores on a leader board." Game Center was announced during an iOS 4 preview event hosted by Apple on April 8, 2010. A preview was released to registered Apple developers in August. It was released on September 8, 2010 with iOS 4.1 on iPhone 4, iPhone 3GS and iPod touch 2nd generation through 4th generation. Game Center made its public debut on the iPad with iOS 4.2.1. There will be no support for the iPhone 3G and original iPhone. However, Game Center is unofficially available on the iPhone 3G via a hack

Jailbreaking
iOS has been subject to a variety of different hacks centered on adding functionality not supported by Apple. Before the 2008 debut of the App Store, the primary reason for jailbreaking was to install third-party native applications.Apple said it would not design software updates specifically to break these native apps (other than applications that perform SIM unlocking); however, with each iOS update the jailbreak appears to no longer work. Since the arrival of the App Store and third-party applications, the focus of the jailbreaking community has shifted. A major focus of jailbreaking is allowing theming, using emulators and community-made tweaks like multitasking, Adobe Flash player, accessing the iPhone file system, and customizing the SpringBoard further. Multitasking is only natively supported on 3rd-generation and newer iOS devices, and applications on the official App Store are not allowed to modify the look of the OS, hence the need for jailbreaking. Groups like greenpois0n, redsn0w, and limera1n have been jailbreaking groups that jailbreak iPhone, iPod, iPad, and Apple TV. Jailbreaking aims at getting fully paid apps for free using Installous, themes, springboard hacks like infinite apps for your dock, and others. Jailbreaking is not illegal and Apple hasn't really made any hard attempts stopping these hackers from jailbreaking their devices but, Apple's warranty will not covers damages caused to the software from a messed up jailbreak. Greenpois0n aims jailbreaks for iOS 4.2.1, redsn0w aims for iPod 3G and 4G and, limera1n aims for every products except iPod 1G. At the this time, any iOS updates above 5.0 are only available for tethered and semi-tethered, which means it requires a computer to boot the device up correctly. Untethered is when computers aren't required for a reboot. There is an official date for untethered jailbreaks for iOS 5.0

Digital Rights Management
The closed and proprietary nature of iOS has garnered criticism, particularly by digital rights advocates such as the Electronic Frontier Foundation, computer engineer and activist Brewster Kahle, Internet-law specialist Jonathan Zittrain, and the Free Software Foundation who protested the iPad's introductory event and have targeted the iPad with their "Defective by Design" campaign.Competitor Microsoft, via a PR spokesman, has also criticized Apple's control over its platform. At issue are restrictions imposed by the design of iOS, namely DRM intended to lock purchased media to Apple's platform, the development model (requiring a yearly subscription to distribute apps developed for the iOS), the centralized approval process for apps, as well as Apple's general control and lockdown of the platform itself. Particularly at issue is the ability for Apple to remotely disable or delete apps at will. Some in the tech community have expressed concern that the locked-down iOS represents a growing trend in Apple's approach to computing, particularly Apple's shift away from machines that hobbyists can "tinker with" and note the potential for such restrictions to stifle software innovation. However, there are some outside of Apple who have voiced support for the iOS closed model. Facebook developer Joe Hewitt, who had previously protested against Apple's control over its hardware as a "horrible precedent", has subsequently argued the locked apps in the iPad are akin to web applications and provide added security.