IOS

iOS (formerly called iPhone OS) is a mobile operating system from Apple Inc. Originally developed for the iPhone, it has since been extended to support other Apple devices including the original Apple TV, iPod touch and iPad. Apple does not license iOS for installation on third-party hardware. iOS was developed from Mac OS X and has since been spun off into iPadOS, tvOS, and watchOS.

Apple's App Store contains more than 650,000 iOS applications, which have collectively been downloaded more than 18 billion times. In May 2010, it accounted for 59% of mobile web data consumption in the United States (including use on the iPod touch and the iPad). By the last quarter of 2010, it had a 26% share of the smartphone operating system units sold, behind both Google's Android and 's.

User interface
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 foundation of Darwin core technology, and is, therefore, a Unix-like operating system by nature. There are four abstraction layers: the Core OS layer, the Core Services layer, the Media layer, and the Cocoa Touch layer. iOS 8.1.3, 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 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.

Home Screen
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.

Notification 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 leaderboard." 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. When jailbroken you get the Cydia app. 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 previous 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 desire for jailbreaking.

Groups like greenpois0n, redsn0w, and limera1n have been jailbreaking groups that jailbreak iPhone, iPod, iPad, and Apple TV. Jailbreaking enables software piracy on iOS, enabling owners of jailbroken devices to install commercial apps for free using AppCake+. However, it also allows the installation of themes, springboard hacks like infinite apps for your dock, and others. Jailbreaking is not illegal and Apple hasn't really made any hard attempts to stop these hackers from jailbreaking their devices, but Apple's warranty will not cover damages caused to the devices 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 product except iPod 1G. At this time, iOS updates above 5.0 are one-way, and cannot be reverted without jailbreaking. Jailbreaks become available in tethered and semi-tethered mode first, which means it requires a computer to boot the device up correctly. Untethered is when computers aren't required for a reboot. There are currently untethered jailbreaks for every version of iOS through iOS 9.3.2 (current).

Decline in interest
In recent years, new features and increased security in iOS have discouraged many jailbreaking pioneers, including Nicholas Allegra (creator of JailbreakMe.com), (creator of Cydia), and Michael Wang (member of iPhone Dev Team). Even Luca Todesco (the hacker behind checkra1n) announced in 2017 that he was publicly disconnecting from the jailbreaking community, though he been known to continue jailbreaking on his own up to iOS 16 and later. Others have continued expressing interest in jailbreaking recent versions of iOS.

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 Zit train, 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. Facebook developer Joe Hewitt protested against Apple's control over its hardware as a "horrible precedent".