iOS

History

In 2005, when Steve Jobs began planning the iPhone, he stated that 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 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 development kit for programmers to build iPhone apps, as well as an App Store within iTunes.

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 the time of its unveiling in January, Steve Jobs claimed: "iPhone runs OS X" and runs "desktop class applications", but at the time of the iPhone's release, the operating system was renamed "iPhone OS". Initially, third-party native applications were not supported. Jobs' reasoning was that developers could build web applications through the Safari web browser that "would behave like native apps on the iPhone". In October 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 held a press event, announcing the iPhone SDK.

The iOS App Store was opened on July 10, 2008, with an initial 500 applications available. This quickly grew to 3,000 in September 2008, 15,000 in January 2009, 50,000 in June 2009, 100,000 in November 2009, 250,000 in August 2010, 650,000 in July 2012, 1 million in October 2013, 2 million in June 2016, and 2.2 million in January 2017. As of March 2016, 1 million apps are natively compatible with the iPad tablet computer. These apps have collectively been downloaded more than 130 billion times. App intelligence firm Sensor Tower estimated that the App Store would reach 5 million apps by 2020.

In September 2007, Apple announced the iPod Touch, a redesigned iPod based on the iPhone form factor. On January 27, 2010, Apple introduced their much-anticipated media tablet, the iPad, featuring a larger screen than the iPhone and iPod Touch, and designed for web browsing, media consumption, and reading, and offering multi-touch interaction with multimedia formats including newspapers, e-books, photos, videos, music, word processing documents, video games, and most existing iPhone apps using a 9.7-inch (25 cm) screen. It also includes a mobile version of Safari for web browsing, as well as access to the App Store, iTunes Library, iBookstore, Contacts, and Notes. Content is downloadable via Wi-Fi and optional 3G service or synced through the user's computer. AT&T was initially the sole U.S. provider of 3G wireless access for the iPad.

Features

Interface

The iOS user interface is based upon direct manipulation, using multi-touch gestures such as swipe, tap, pinch, and reverse pinch. Interface control elements include sliders, switches, and buttons. 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 between portrait and landscape mode). Various accessibility described in § Accessibility functions enable users with vision and hearing disabilities to properly use iOS.

iOS devices boot to the lock screen. The lock screen shows the time and a user's lock screen widgets, which display timely information from apps. The lock screen also has two buttons, called Controls, which are only available on iPhone. These default to flashlight and camera, but they can be customized to any control available in Control Center and can also be removed. Upon unlock, a user is directed to the home screen, which is the primary navigation and information "hub" on iOS devices, analogous to the desktop found on personal computers. iOS home screens are typically made up of app icons and widgets; app icons launch the associated app, whereas widgets display live, auto-updating content, such as a weather forecast, the user's email inbox, or a news ticker directly on the home screen.

Along the top of the screen is a status bar, showing information about the device and its connectivity. The Control Center can be "pulled" down from the top right of the notch or Dynamic Island on iPhones with Face ID, or can be "pulled" up from the bottom to top of the screen on iPhones with Touch ID, giving access to various toggles to manage the device more quickly without having to open the Settings. It is possible to manage brightness, volume, wireless connections, music player, etc.

Scrolling from the top left to the bottom (or top to bottom on iPhones with Touch ID) will open the Notification Center, which in the latest versions of iOS is very similar to the lock screen. It displays notifications in chronological order and groups them by application. From the notifications of some apps it is possible to interact directly, for example by replying to a message directly from it. Notifications are sent in two modes, critical alerts that are displayed on the lock screen and signaled by a distinctive sound and vibration (e.g. emergency alerts or severe weather alerts), accompanied by a warning banner and the app badge icon, and standard alerts which use a default sound and vibration. Both can be found in the Notification Center, and show for a set amount of time on the lock screen (unless the user has Notification Center allowed when locked).

Storage

iOS enforces strict sandboxing to maintain security and privacy. Apps are generally limited to accessing their own containers and specific system-provided directories, such as the Photos library. To access files outside of their sandbox, iOS uses mechanisms like document pickers, file providers, and app extensions.

iOS 8 introduced the Document Picker and Document Provider extensions as part of the document interaction controller. This allows apps to open, save, and interact with documents stored in a central location or cloud storage services.

With iOS 11, Apple introduced the Files app and the File Provider extension, providing a central location for users to manage and organize their files. Apps can integrate with the Files app to make their documents accessible and editable directly from the Files app.

The storage of iOS devices can be expanded through iCloud, the Apple's cloud-based storage solution that provides 5GB of storage for free to all users, while other plans require a paid subscription. iCloud Drive allows users to store various types of files, such as documents, presentations, and spreadsheets, in the cloud. These files can be accessed across multiple devices as long as the user is signed in with the same Apple ID.

Accessibility

iOS offers various accessibility features to help users with vision and hearing disabilities. One major feature, VoiceOver, provides a voice reading information on the screen, including contextual buttons, icons, links and other user interface elements, and allows the user to navigate the operating system through gestures. Any apps with default controls and developed with a UIKit framework gets VoiceOver functionality built in. One example includes holding up the iPhone to take a photo, with VoiceOver describing the photo scenery. As part of a "Made for iPhone" program, introduced with the release of iOS 7 in 2013, Apple has developed technology to use Bluetooth and a special technology protocol to let compatible third-party equipment connect with iPhones and iPads for streaming audio directly to a user's ears. Additional customization available for Made for iPhone products include battery tracking and adjustable sound settings for different environments. Apple made further efforts for accessibility for the release of iOS 10 in 2016, adding a new pronunciation editor to VoiceOver, adding a Magnifier setting to enlarge objects through the device's camera, software TTY support for deaf people to make phone calls from the iPhone, and giving tutorials and guidelines for third-party developers to incorporate proper accessibility functions into their apps.

In 2012, Liat Kornowski from The Atlantic wrote that "the iPhone has turned out to be one of the most revolutionary developments since the invention of Braille", and in 2016, Steven Aquino of TechCrunch described Apple as "leading the way in assistive technology", with Sarah Herrlinger, Senior Manager for Global Accessibility Policy and Initiatives at Apple, stating that "We see accessibility as a basic human right. Building into the core of our products supports a vision of an inclusive world where opportunity and access to information are barrier-free, empowering individuals with disabilities to achieve their goals".

Criticism has been aimed at iOS depending on both internet connection (either WiFi or through iTunes) and a working SIM card upon first activation. This restriction has been loosened in iOS 12, which no longer requires the latter.

Multitasking

Multitasking for iOS was first released in June 2010 along with the release of iOS 4. Only certain devices—iPhone 4, iPhone 3GS, and iPod Touch 3rd generation—were able to multitask. The iPad did not get multitasking until iOS 4.2.1 in that November.

The implementation of multitasking in iOS has been criticized for its approach, which limits the work that applications in the background can perform to a limited function set and requires application developers to add explicit support for it.

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:

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

In iOS 5, three new background APIs were introduced:

Newsstand – application can download content in the background to be ready for the user

Siri

Siri () is a virtual assistant integrated into iOS. The assistant uses voice queries and a natural-language user interface to answer questions, make recommendations, and perform actions by delegating requests to a set of Internet services. The software adapts to users' individual language usages, searches, and preferences, with continuing use. Returned results are individualized.

Originally released as an app for iOS in February 2010, it was acquired by Apple two months later, and then integrated into iPhone 4S at its release in October 2011. At that time, the separate app was also removed from the iOS App Store.

Siri supports a wide range of user commands, including performing phone actions, checking basic information, scheduling events and reminders, handling device settings, searching the Internet, navigating areas, finding information on entertainment, and is able to engage with iOS-integrated apps. With the release of iOS 10 in 2016, Apple opened up limited third-party access to Siri, including third-party messaging apps, as well as payments, ride-sharing, and Internet calling apps. With the release of iOS 11, Apple updated Siri's voices for more clear, human voices, it now supports follow-up questions and language translation, and additional third-party actions. iOS 17 enabled users to activate Siri by simply saying "Siri", while the previous command, "Hey Siri", is still supported.

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.

Supported processors

The instruction set architectures supported by iOS are the ARM architectures. With currently supported ARM architectures being various versions of the ARMv8 and ARMv9 architectures. iOS, prior to the release of iOS 7 in 2013, only supported devices with 32-bit ARM processors supporting the ARMv6 or ARMv7-A architectures, however iOS 7 added full support for the 64-bit architecture (including a native 64-bit kernel, libraries, drivers as well as all built-in applications), after Apple announced that they were switching to 64-bit ARMv8-A processors with the introduction of the Apple A7 chip. 64-bit support has been enforced for all app submissions made to the App Store since 2015; specifically, new apps since February 2015, and all updates to apps since June 1, 2015. iOS 11, released in 2017, dropped support for all iOS devices with 32-bit ARM processors as well as 32-bit applications, making iOS 64-bit only.

Devices

iOS powers almost exclusively Apple hardware. It is used for all iPhones and iPod Touch devices. Further, Apple Watches, Apple TVs, and iPads either also use iOS for some models or use OSes based on iOS for other models.

Development

The iOS software development kit (SDK) allows for the development of mobile apps that can run on iOS.

While originally developing iPhone prior to its unveiling in 2007, Apple's then-CEO Steve Jobs did not intend to let third-party developers build native apps for iOS, instead directing them to make web applications for the Safari web browser. However, backlash from developers prompted the company to reconsider, with Jobs announcing in October 2007 that Apple would have a software development kit available for developers by February 2008. The SDK was released on March 6, 2008.

The SDK is a free download for users of Mac personal computers. It is not available for Microsoft Windows PCs. The SDK contains sets giving developers access to various functions and services of iOS devices, such as hardware and software attributes. It also contains an iPhone simulator to mimic the look and feel of the device on the computer while developing. New versions of the SDK accompany new versions of iOS. In order to test applications, get technical support, and distribute apps through App Store, developers are required to subscribe to the Apple Developer Program.

Combined with Xcode, the iOS SDK helps developers write iOS apps using officially supported programming languages, including Swift and Objective-C. Other companies have also created tools that allow for the development of native iOS apps using their respective programming languages.

Update history and schedule

Apple provides major updates to the iOS operating system annually. Since iOS 5, the primary method of delivery has been over-the-air. Updates are also available using iTunes on older versions of macOS and Windows, using Finder on macOS starting with macOS Catalina, and using the Apple Devices app on Windows starting with Windows 10 version 22H2.

The device checks an XML-based PLIST file on mesu.apple.com for updates. Updates are delivered as unencrypted ZIP files. Updates are checked for regularly, and are downloaded and installed automatically if enabled. Otherwise, the user can install them manually or are prompted to allow automatic installation overnight if plugged in and connected to Wi-Fi.

iPod Touch users originally had to pay for system software updates due to accounting rules that designated it not a "subscription device" like the iPhone or Apple TV, causing many iPod Touch owners not to update. In September 2009, a change in accounting rules won tentative approval, affecting Apple's earnings and stock price, and allowing iPod Touch updates to be delivered free of charge.

Apple significantly extended the cycle of updates for iOS-supported devices over the years. The iPhone (1st generation) and iPhone 3G only received two major iOS updates, while later models had support for three to seven major updates.

XNU kernel

iOS uses the XNU kernel included in the Darwin operating system and used by macOS, adapted to work with devices that run iOS. It is additionally used as the kernel for Apple's other platforms and operating systems, including iPadOS, watchOS, visionOS, and tvOS, and also serves as the kernel used by the software powering the HomePod range of smart speakers. iOS 18, the second-to-latest stable version of iOS, uses version 24 of Darwin. Darwin, and by definition XNU, is open source software dual-licensed under the 3-clause BSD license for components developed specifically for BSD, and the Apple Public Source License (APSL) for components of the operating system and kernel that have been developed by Apple; however, XNU is licensed specifically under the APSL.

Since the release of iOS 6 in 2012, the kernel uses kernel address space layout randomization (KASLR), a technology and security technique introduced in OS X Mountain Lion and included in later versions of macOS that makes it harder to exploit known and future memory corruption security vulnerabilities by randomizing the memory addresses used by the kernel.

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 would 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.

When a device is booting, it loads Apple's own kernel initially, so a jailbroken device must be exploited and have the kernel patched each time it is booted up.

There are different types of jailbreak. An untethered jailbreak uses exploits that are powerful enough to allow the user to turn their device off and back on at will, with the device starting up completely, and the kernel will be patched without the help of a computer – in other words, it will be jailbroken even after each reboot.

However, some jailbreaks are tethered. A tethered jailbreak is only able to temporarily jailbreak the device during a single boot. If the user turns the device off and then boots it back up without the help of a jailbreak tool, the device will no longer be running a patched kernel, and it may get stuck in a partially started state, such as Recovery Mode. In order for the device to start completely and with a patched kernel, it must be "re-jailbroken" with a computer (using the "boot tethered" feature of a tool) each time it is turned on. All changes to the files on the device (such as installed package files or edited system files) will persist between reboots, including changes that can only function if the device is jailbroken (such as installed package files).

In more recent years, two other solutions have been created – semi-tethered and semi-untethered.

A semi-tethered solution is one where the device is able to start up on its own, but it will no longer have a patched kernel, and therefore will not be able to run modified code. It will, however, still be usable for normal functions, just like stock iOS. To start with a patched kernel, the user must start the device with the help of the jailbreak tool.

Unlocking

Initially most wireless carriers in the US did not allow iPhone owners to unlock it for use with other carriers. However AT&T allowed iPhone owners who had satisfied contract requirements to unlock their iPhone. Instructions to unlock the device are available from Apple, but it is ultimately at the sole discretion of the carrier to authorize unlocking the device. This allows the use of a carrier-sourced iPhone on other networks. Modern versions of iOS and the iPhone fully support LTE across multiple carriers wherever the phone was purchased. Programs to remove SIM lock restrictions are available, but are not supported by Apple, and most often not a permanent unlock – a soft unlock, which modifies the iPhone so that the baseband will accept the SIM card of any GSM carrier. SIM unlocking is not jailbreaking, but a jailbreak is also required for these unofficial software unlocks.

The legality of software unlocking varies in each country; for example, in the US, there is a DMCA exemption for unofficial software unlocking of devices purchased before January 26, 2013.

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.

Security and privacy

iOS utilizes many security features in both hardware and software.

Reception

Market share

iOS is the second most popular mobile operating system in the world, after Android. Sales of iPads in recent years are also behind Android, while, by web use (a proxy for all use), iPads (using iOS) are still the most popular.

At WWDC 2014, Tim Cook said 800 million devices had been sold by June 2014. During Apple's quarterly earnings call in January 2015, the company announced that they had sold over one billion iOS devices since 2007.

By February 2023, there were 2 billion devices activated, and 1.5 billion iPhones had been sold since 2007.

By late 2011, iOS accounted for 60% of the market share for smartphones and tablets. By the end of 2014, iOS accounted for 14.8% of the smartphone market and 27.6% of the tablet and two-in-one market. In May 2023, StatCounter reported iOS was used on 31.44% of smartphones and 55.75% of tablets worldwide, measured by internet usage instead of sales.

In the third quarter of 2015, research from Strategy Analytics showed that iOS adoption of the worldwide smartphone market was at a record low 12.1%, attributed to lackluster performance in China and Africa. Android accounted for 87.5% of the market, with Windows Phone and BlackBerry accounting for the rest.