IOS

iOS (previously iPhone OS) is a mobile operating system developed and distributed by Apple Inc.

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 (September 2010). Unlike Microsoft's Windows Phone and Google's Android, Apple does not license iOS for installation on non-Apple hardware. , Apple's App Store contained more than 1 million iOS applications, 500,000 of which were optimised for iPad. These apps have collectively been downloaded more than 60 billion times. It had a 21% share of the smartphone mobile operating system units shipped in the fourth quarter of 2012, behind Google's Android. At the half of 2012, there were 410 million devices activated. According to the special media event held by Apple on September 12, 2012, 400 million devices had been sold by June 2012.

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. 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 various application frameworks. iOS is Apple's mobile version of the OS X operating system used on Apple computers.

Major versions of iOS are released annually. The current release, iOS 7, was released on September 18, 2013. 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 7.0.4), dedicates 1–1.5 GB of the device's flash memory for the system partition, using roughly 800 MB of that partition (varying by model) for iOS itself. It runs on the iPhone 4 and later, 2nd-generation iPad and later, all models of the iPad Mini, the 5th-generation iPod Touch, and Apple TV.

History
The operating system was unveiled with the iPhone at the Macworld Conference & Expo, 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' reasoning was 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".

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.

By late 2011, iOS accounted for 60% of the market share for smartphones and tablet computers. By the end of 2012, iOS accounted for 21% of the smartphone OS market and 43.6% of the tablet OS market.

Software updates
Apple provides major updates to the iOS operating system approximately once a year over iTunes and also, since iOS version 5.0, over the air. The latest version is iOS 7.0.4, which is available for the iPhone 4, iPhone 4S, iPhone 5, iPhone 5C, iPhone 5S, iPad 2, the third-generation iPad, the fourth-generation iPad, the iPad Air, the first-generation iPad Mini, the second-generation iPad Mini, and the fifth-generation iPod Touch. Before iOS 4's release in 2010, iPod Touch users had to pay for system software updates. Apple claimed that this was the case, because the iPod Touch was not a 'subscription device' like the iPhone (i.e. it was a one-off purchase). Apple said it had 'found a way' to deliver software updates for free to iPod Touch users at WWDC 2010, when iOS 4 was unveiled.

Home Screen
The home screen (rendered by and also known as "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 unlocks the device or presses the "Home" button (a physical button on the device) whilst in another app. The screen's background can be customized with other customizations available through jailbreaking. 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. When a passcode is set and a user switches on the device, the passcode must be entered at the Lock Screen before access to the Home Screen is granted.

Since iOS version 3.0, a Spotlight Search function has been available on the leftmost page of the home screen page allowing users to search through media (music, videos, podcasts, etc.), applications, e-mails, contacts, messages, reminders, calendar events, and similar files. Third-party app files were not, and still are not, searchable using the Spotlight feature. In iOS 7, this feature can be accessed by pulling down anywhere on the screen.

In iOS 3.2 or later and with a supported device, the user can set a picture as the background of the home screen. This feature is only available on third-generation devices or newer – iPhone 3GS or newer, iPod Touch 3rd gen. or newer, and all iPad models.

Researchers found that users organize icons on their homescreens based on usage-frequency and relatedness of the applications, as well as for reasons of usability and aesthetics.

Folders
With iOS 4 came the introduction of a simple folder system. When applications are in "jiggle mode", any two (with the exception of Newsstand in iOS 5 and later, which acts like a folder ) 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 4S and earlier and iPod Touch, 16 on iPhone 5, and 20 on iPad. A title for the folder is automatically selected by the category of applications inside, but the name can also be edited by the user. When apps inside folders receive badges, the numbers shown by the badges is added up and shown on the folder. Folders cannot be put into other folders, but through exploiting iOS glitches, Newsstand and other folders can be forced to be placed into a folder. This is handy for some users who find the Newsstand functionality useless. However, upon attempting to open a folder/the Newsstand within a folder, the SpringBoard will crash.

iOS 7 updated the folders with pages like on the SpringBoard. Each page can hold nine apps on all devices and the Newsstand app is able to be placed into folders, as it was redesigned to act as an application. A similar glitch appears, enabling folders to be nested within folders without the SpringBoard crashing, with increasing nesting capability.

Notification Center
Before iOS 5, notifications were delivered in blue dialog box. This system of notification management was greatly criticised. In the iOS 5 update, the notifications feature was completely redesigned. Notifications collate in a window which can be dragged down from the top of the screen. If a user touches a received notification, the application that sent the notification will be opened. Notifications are now delivered in small banners that appear over the status bar. The old method of delivering notifications is still available from Notification Settings if the user wishes to enable it for some or all applications.

When an app sends a notification whilst closed, a red badge will appear on its icon. This badge tells the user, at a glance, how many notifications that app has sent. Opening the app clears the badge.

Included applications
The iOS home screen contains these default "apps". Some of these applications are hidden by default and accessed by the user through the Settings app or another method—for instance, Nike+iPod is activated through the Settings app. Many of these apps, such as Safari, the App Store, and Siri, can also be disabled in the Restrictions section of the Settings app.

On the iPhone and iPod Touch, apps such as Voice Memos, Contacts, Calculator, and Compass are in one folder called "Utilities" in iOS 4 and above. Many of the included applications are designed to share data (e.g., a phone number can be selected from an email and saved as a contact or dialed for a phone call). For the iOS 7 update, the folder name was changed to "Extras".

"iMessage" is available on all iOS devices running iOS 5 or above. iMessage is effectively a version of the Messages app that sends free text or multimedia messages to other iOS devices (similar to BlackBerry Messenger).

Panoramic photography is available only on iPhone 4S and later models, and the fifth generation iPod Touch.

The bottom row of applications, called the dock, is used to delineate the iPhone's main purposes: originally Phone, Mail, Safari, iPod. Starting with iOS 5, the iPod app was split into two apps, Music and Videos, as it always has been on the iPod Touch, and the Music app replaced the iPod app in the dock. In iOS 7, the iPhone gains a dedicated FaceTime app (previously integrated into the Phone app), as it had been on the iPod Touch and iPad since iOS 4.

Starting January 2008, the iPod Touch retains the same applications that are present by default on the iPhone, with the exception of the Phone and Compass (and also previously, Messages before iOS 5 and Camera before the fourth-generation iPod Touch) apps. The original dock layout was Music, Videos, Photos, and iTunes. In iPhone OS 3, the layout was changed to Music, Videos, Safari, and App Store. For the fourth-generation iPod Touch, it includes FaceTime and Camera, and the dock layout had changed to Music, Mail, Safari, Videos, with the release of iOS 4. With the release of the new fifth-generation iPod Touch and iOS 6, the dock layout was changed to Messages, Mail, Safari, Music, similar to the iPhone.

The iPad and iPad Mini come with the same applications as the iPod Touch, excluding Stocks, Weather, Calculator, and the Nike + iPod app (and also previously, Clock before iOS 6). Additionally, starting with the iPad 2, they have the unique Photo Booth app. Most of the default applications, such as Safari and Mail, are completely rewritten to take advantage of the iPad's and iPad Mini's larger displays. The original dock layout was Safari, Mail, Photos, iPod. Separate music and video apps are provided, as on the iPod Touch, although (as on the iPhone) the music app was named "iPod". In iOS 5, it was changed to "Music" and the dock layout became Safari, Mail, Photos, Music. In iOS 6, Videos replaced Photos in the dock. In iOS 7, the default dock layout was changed to match that of the iPod Touch.

Multitasking


Before iOS 4, multitasking was limited to a selection of the applications Apple included on the device. Users could, however "jailbreak" their device in order to unofficially multitask. Starting with iOS 4, on third-generation and newer iOS devices, multitasking is supported through seven background APIs: In iOS 5, three new background APIs were introduced: In iOS 7, Apple introduced a new multitasking feature, providing all apps with the ability to perform background updates. This feature prefers to update the user's most frequently used apps and prefers to use WiFi networks over a cellular network, without markedly reducing the device's battery life.
 * 1) Background audio – application continues to run in the background as long as it is playing audio or video content
 * 2) Voice over IP – application is suspended when a phone call is not in progress
 * 3) Background location – application is notified of location changes
 * 4) Push notifications
 * 5) Local notifications – application schedules local notifications to be delivered at a predetermined time
 * 6) Task completion – application asks the system for extra time to complete a given task
 * 7) Fast app switching – application does not execute any code and may be removed from memory at any time
 * 1) Newsstand – application can download content in the background to be ready for the user
 * 2) External Accessory – application communicates with an external accessory and shares data at regular intervals
 * 3) Bluetooth Accessory – application communicates with a bluetooth accessory and shares data at regular intervals

Switching applications
In iOS 4.0 to iOS 6.x, double-clicking the home button activates the application switcher. A scrollable dock-like interface appears from the bottom, moving the contents of the screen up. Choosing an icon switches to an application. To the far left are icons which function as music controls, a rotation lock, and on iOS 4.2 and above, a volume controller. Holding the icons briefly makes them "jiggle" (similarly to the homescreen) and allows the user to force quit the applications by simply tapping the red minus circle that appears at the corner of the app's icon.

With the introduction of iOS 7, double clicking the home button also activates the application switcher. However, unlike previous versions it displays screenshots of open applications on top of the icon and horizontal scrolling allows for browsing through previous apps, and it is possible to close applications by dragging them up, similar to how WebOS handled multiple cards.

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, the iPad Mini, and the third-generation and later iPads.

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." iOS 5 and above adds support for profile photos.

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 is no support for the iPhone 3G, original iPhone and the first-generation iPod Touch (the latter two devices did not have Game Center because they did not get iOS 4). However, Game Center is unofficially available on the iPhone 3G via a hack.

Development
The applications must be written and compiled specifically for iOS and the 64-bit ARM architecture or previous 32-bit one. The Safari web browser supports web applications as with other web browsers. Authorized third-party native applications are available for devices running iOS 2.0 and later through Apple's App Store. A Q3 2013 study found that mobile developers use iOS as a primary platform more than Android (59% vs. 49%), despite Android being a more popular platform overall.

SDK
On October 17, 2007, in an open letter posted to Apple's "Hot News" weblog, Steve Jobs announced that a software development kit (SDK) would be made available to third-party developers in February 2008. The SDK was released on March 6, 2008, and allows developers to make applications for the iPhone and iPod Touch, as well as test them in an "iPhone simulator". However, loading an application onto the devices is only possible after paying an iPhone Developer Program fee.

The fees to join the respective developer programs for iOS and OS X were each set at $99.00 per year. As of July 20, 2011, Apple released Xcode on its Mac App Store free to download for all OS X Lion users, instead of as a standalone download. Users can create and develop iOS and OS X applications using a free copy of Xcode; however, they cannot test their applications on a physical iOS device, or publish them to the App store, without first paying the yearly $99.00 iPhone Developer or Mac Developer Program fee.

Since the release of Xcode 3.1, Xcode is the development environment for the iOS SDK. iOS applications, like many of the higher-level frameworks and applications that are part of iOS and OS X, are written in Objective-C.

Developers are able to set any price above a set minimum for their applications to be distributed through the App Store, keeping 70% for the developer, and leaving 30% for Apple. Alternatively, they may opt to release the application for free and need not pay any costs to release or distribute the application except for the membership fee.

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 the native iOS App Store, the primary motive for jailbreaking was to install third-party native applications, which was not allowed by Apple at the time. 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. 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. It should be noted that depending on the method used, the effects of jailbreaking may be permanent, or can be restored to the original state.

In 2010, the Electronic Frontier Foundation (EFF) successfully convinced the U.S. Copyright Office to allow an exemption to the general prohibition on circumvention of copyright protection systems under the Digital Millennium Copyright Act (DMCA). The exemption allows jailbreaking of iPhones for the sole purpose of allowing legally obtained applications to be added to the iPhone. The exemption does not affect the contractual relations between Apple and an iPhone owner, for example, jailbreaking voiding the iPhone warranty; however, it is solely based on Apple's discretion on whether they will fix jailbroken devices in the event that they need to be repaired. At the same time, the Copyright Office exempted unlocking an iPhone from DMCA's anticircumvention prohibitions. Unlocking an iPhone allows the iPhone to be used with any wireless carrier using the same GSM or CDMA technology for which the particular phone model was designed to operate.

Unlocking
Initially most wireless carriers did not allow iPhone owners to unlock an iPhone for use with other carriers. AT&T Mobility allows iPhone owners who have satisfied the requirements of their contract to unlock their iPhone. Instructions to unlock the device are available from Apple, but it is ultimately the sole discretion of the carrier to authorize the device to be unlocked. This allows the use of a carrier sourced iPhone on other networks. However, because T-Mobile primarily uses a different band than AT&T for its 3G data signals, the iPhone will only work at 3G speeds on the T-Mobile 1900 MHz network. There are programs to break these restrictions, but are not supported by Apple and most often not a permanent unlock, known as soft-unlock.

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, criticized Apple's control over its platform.

At issue are restrictions imposed by the design of iOS, namely digital rights management (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. Former Facebook developer Joe Hewitt protested against Apple's control over its hardware as a "horrible precedent" but praised iOS's sandboxing of apps.

Kernel
The iOS kernel is based on Darwin OS. The original iPhone OS (1.0) up to iPhone OS 3.1.3 used Darwin 9.0.0d1. iOS 4 was based on Darwin 10.0.0. iOS 5 was based on Darwin 11.0.0. iOS 6 was based on Darwin 13.0.0. iOS 7 is based on Darwin 14.0.0 (Darwin Kernel Version 14.0.0:Fri Sep 27 00:44:15 PDT 2013;root:xnu-2423.3.12~1/RELEASE_ARM). )