iOS(Redirected from IOS (Apple))
iOS (formerly iPhone OS) is a mobile operating system created and developed by Apple Inc. exclusively for its hardware. It is the operating system that presently powers many of the company's mobile devices, including the iPhone, iPad, and iPod Touch. It is the second most popular mobile operating system globally after Android.
iOS 11 developer beta 6 running on an iPhone 7 Plus
|Written in||C, C++, Objective-C, Swift|
|OS family||Unix-like, based on Darwin (BSD), macOS|
|Source model||Closed source|
|Initial release||June 29, 2007|
|Latest release||10.3.3 (14G60) (July 19, 2017 ) [±]|
|Latest preview||11.0 beta 6 (15A5354b) (August 14, 2017 ) [±]|
|Marketing target||Smartphones, tablet computers, portable media players|
|Available in||40 languages|
|Update method||iTunes or OTA (iOS 5 or later)|
|Kernel type||Hybrid (XNU)|
|Default user interface||Cocoa Touch (multi-touch, GUI)|
|License||Proprietary software except for open-source components|
Originally unveiled in 2007 for the iPhone, iOS has been extended to support other Apple devices such as the iPod Touch (September 2007) and the iPad (January 2010). As of January 2017[update], Apple's App Store contains more than 2.2 million iOS applications, 1 million of which are native for iPads. These mobile apps have collectively been downloaded more than 130 billion times.
The iOS user interface is based upon 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 between portrait and landscape mode). Apple has been significantly praised for incorporating thorough accessibility functions into iOS, enabling users with vision and hearing disabilities to properly use its products.
Major versions of iOS are released annually. The current version, iOS 10, was released on September 13, 2016. It is available for the iPhone 5 and later iPhone models, the fourth-generation iPad, the iPad Air and iPad Air 2, the iPad Pro, the iPad Mini 2 and later iPad Mini models, and the sixth-generation iPod Touch. Its successor, iOS 11, was announced on June 5, 2017, with a consumer release set for late 2017.
In 2005, when Steve Jobs began planning the iPhone, 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 the 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 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[update], 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 has estimated that the App Store will reach 5 million apps by the year 2020.
In September 2007, Apple announced the iPod Touch, a redesigned iPod based on the iPhone form factor. In January 2010, Apple announced the iPad, featuring a larger screen than the iPhone and iPod Touch, and designed for web browsing, media consumption, and reading.
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.
Apple provides major updates to the iOS operating system annually via iTunes and also, for iOS 5 and later, over-the-air. The latest version is iOS 10, released on September 13, 2016. It is available for iPhone 5 and later, fourth-generation iPad, first- and second-generation iPad Air, iPad Pro, iPad Mini 2 and later, and sixth-generation iPod Touch.
Originally, iPod Touch users had to pay for system software updates. This was due to accounting rules making the device not a "subscription device" like iPhone or Apple TV, and significant enhancements to the device required payments. The requirement to pay to upgrade caused iPod Touch owners to stay away from updates. However, in September 2009, a change in accounting rules won tentative approval, significantly affecting both Apple's earnings and stock price, and allowing iPod Touch updates to be delivered for free.
The home screen, rendered by SpringBoard, displays application icons and a dock at the bottom where users can pin their most frequently used apps. The home screen appears whenever the user unlocks the device or presses the physical "Home" button whilst in another app. Before iOS 4 on the iPhone 3GS (or later), the screen's background could be customized only through jailbreaking, but can now be changed out-of-the-box. 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.
In iPhone OS 3, Spotlight was introduced, allowing users to search media, apps, emails, contacts, messages, reminders, calendar events, and similar content. In iOS 7 and later, Spotlight is accessed by pulling down anywhere on the home screen (except for the top and bottom edges that open Notification Center and Control Center). In iOS 9, there are two ways to access Spotlight. As with iOS 7 and 8, pulling down on any homescreen will show Spotlight. However, it can also be accessed as it was in iOS 3 – 6. This gives a Spotlight endowed with Siri suggestions, which include app suggestions, contact suggestions and news. In iOS 10, Spotlight is at the top of the now-dedicated "Today" panel.
Since iOS 3.2, users are able to set a background image for the Home screen. This feature is only available on third-generation devices—iPhone 3GS, third-generation iPod touch (iOS 4.0 or newer), all iPad models (since iOS 3.2)—or newer.
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.
iOS originally used Helvetica as the system font. With the release of the iPhone 4 and iOS 4, iOS switched to Helvetica Neue with Retina Displays, but retained Helvetica as the system font for older devices. iOS 7 provided the ability to scale text or switch to Neue Bold as the default system font, as accessibility options. iOS 9 changed the font to San Francisco, an Apple-designed font for maximum legibility on computer and mobile displays, originally introduced as the system font for the Apple Watch.
iOS 4 introduced folders, which can be created by dragging an application on top of another, and from then on, more items can be added to the folder using the same procedure. It can be 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, though an unofficial workaround exists that enables folders to be nested within folders. iOS 7 updated the folders with pages like on the SpringBoard. Each page can hold nine apps, and the Newsstand app is now able to be placed into a folder.
Before iOS 5, notifications were delivered in a modal window and couldn't be viewed after being dismissed. In iOS 5, Apple introduced Notification Center, which allows users to view a history of notifications. The user can tap a notification to open its corresponding app, or clear it. Notifications are now delivered in banners that appear briefly at the top of the screen. If a user taps a received notification, the application that sent the notification will be opened. Users can also choose to view notifications in modal alert windows by adjusting the application's notification settings. Introduced with iOS 8, widgets are now accessible through the Notification Center, defined by 3rd parties.
When an app sends a notification while closed, a red badge appears on its icon. This badge tells the user, at a glance, how many notifications that app has sent. Opening the app clears the badge.
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".
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 November. Currently, multitasking is supported on iPhone 3GS+, iPod Touch 3rd generation+, and all iPad models.
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
- External Accessory – application communicates with an external accessory and shares data at regular intervals
- Bluetooth Accessory – application communicates with a bluetooth accessory and shares data at regular intervals
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.
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.
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.
With the introduction of iOS 9, the application switcher received a significant visual change; whilst still retaining the card metaphor introduced in iOS 7, the application icon is smaller, and appears above the screenshot (which is now larger, due to the removal of "Recent and Favorite Contacts"), and each application "card" overlaps the other, forming a rolodex effect as the user scrolls. Now, instead of the home screen appearing at the leftmost of the application switcher, it appears rightmost.
In iOS 4.0 to iOS 6.x, briefly holding the icons in the application switcher makes them "jiggle" (similarly to the homescreen) and allows the user to force quit the applications by tapping the red minus circle that appears at the corner of the app's icon. Clearing applications from multitasking stayed the same from iOS 4.0 through 6.1.6, the last version of iOS 6.
As of iOS 7, the process has become faster and easier. In iOS 7, instead of holding the icons to close them, they are closed by simply swiping them upwards off the screen. Up to three apps can be cleared at a time compared to one in versions up to iOS 6.1.6.
Task completion allows apps to continue a certain task after the app has been suspended. As of iOS 4.0, apps can request up to ten minutes to complete a task in the background. This doesn't extend to background up- and downloads though (e.g. if you start a download in one application, it won't finish if you switch away from the application).
Siri (pronounced //) is an intelligent personal 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 upcoming release of iOS 11, Apple will update Siri's voices for more clear, human voices, will support follow-up questions and language translation, and additional third-party actions.
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.
The main hardware platform for iOS is the ARM architecture. iOS releases up till iOS 6 can only be run on iOS devices with 32-bit ARM processors (ARMv6 and ARMv7-A architectures). In 2013, iOS 7 was released with full 64-bit support (which includes 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 was also enforced for all apps in the App Store; All new apps submitted to the App Store with a deadline of February 2015, and all app updates submitted to the App Store with a deadline of June 1, 2015. Apple is set to release iOS 11 in late 2017, which drops support for all iOS devices with 32-bit ARM processors as well as 32-bit applications, making iOS 64-bit only.
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.
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 most popular.
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 February 2015, StatCounter reported iOS was used on 23.18% of smartphones and 66.25% 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.
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 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 SpringBoard. An additional motivation is that it may enable the installation of pirated apps. 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. Depending on the method used, the effects of jailbreaking may be permanent or temporary.
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.
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 have satisfied contract requirements 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, 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 - a 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.
The iOS kernel is the XNU kernel of Darwin. 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. iOS 5 was based on Darwin 11. iOS 6 was based on Darwin 13. iOS 7 and iOS 8 are based on Darwin 14. iOS 9 is based on Darwin 15. iOS 10 is based on Darwin 16.
iOS utilizes many security features in both hardware and software. Below are summaries of the most prominent features.
Before fully booting into iOS, there is low-level code that runs from the Boot ROM. Its task is to verify that the Low-Level Bootloader is signed by the Apple Root CA public key before running it. This process is to ensure that no malicious or otherwise unauthorized software can be run on an iOS device. After the Low-Level Bootloader finishes its tasks, it runs the higher level bootloader, known as iBoot. If all goes well, iBoot will then proceed to load the iOS kernel as well as the rest of the operating system.
The Secure Enclave is a coprocessor found in iOS devices that contain Touch ID. It has its own secure boot process to ensure that it is completely secure. A hardware random number generator is also included as a part of this coprocessor. Each device's Secure Enclave has a unique ID that is given to it when it is made and cannot be changed. This identifier is used to create a temporary key that encrypts the memory in this portion of the system. The Secure Enclave also contains an anti-replay counter to prevent brute force attacks.
iOS devices can have a passcode that is used to unlock the device, make changes to system settings, and encrypt the device's contents. Until recently, these were typically four numerical digits long. However, since unlocking the devices with a fingerprint by using Touch ID has become more widespread, six-digit passcodes are now the default on iOS with the option to switch back to four or use an alphanumeric passcode.
Touch ID is a fingerprint scanner that is embedded in the home button and can be used to unlock the device, make purchases, and log into applications among other functions. When used, Touch ID only temporarily stores the fingerprint data in encrypted memory in the Secure Enclave, as described above. There is no way for the device's main processor or any other part of the system to access the raw fingerprint data that is obtained from the Touch ID sensor.
Address Space Layout Randomization
Address Space Layout Randomization (ASLR) is a low-level technique of preventing memory corruption attacks such as buffer overflows. It involves placing data in randomly selected locations in memory in order to make it harder to predict ways to corrupt the system and create exploits. ASLR makes app bugs more likely to crash the app than to silently overwrite memory, regardless of whether the behavior is accidental or malicious.
iOS utilizes the ARM architecture's Execute Never (XN) feature. This allows some portions of the memory to be marked as non-executable, working alongside ASLR to prevent buffer overflow attacks including return-to-libc attacks.
As mentioned above, one use of encryption in iOS is in the memory of the Secure Enclave. When a passcode is utilized on an iOS device, the contents of the device are encrypted. This is done by using a hardware AES 256 implementation that is very efficient because it is placed directly between the flash storage and RAM.
The iOS keychain is a database of login information that can be shared across apps written by the same person or organization. This service is often used for storing passwords for web applications.
Third-party applications such as those distributed through the App Store must be code signed with an Apple-issued certificate. This continues the chain of trust all the way from the Secure Boot process as mentioned above to the actions of the applications installed on the device by users. Applications are also sandboxed, meaning that they can only modify the data within their individual home directory unless explicitly given permission to do otherwise. For example, they cannot access data that is owned by other user-installed applications on the device. There is a very extensive set of privacy controls contained within iOS with options to control apps' ability to access a wide variety of permissions such as the camera, contacts, background app refresh, cellular data, and access to other data and services. Most of the code in iOS, including third-party applications, run as the "mobile" user which does not have root privileges. This ensures that system files and other iOS system resources remain hidden and inaccessible to user-installed applications.
iOS supports TLS with both low- and high-level APIs for developers. By default, the App Transport Security framework requires that servers use at least TLS 1.2. However, developers are free to override this framework and utilize their own methods of communicating over networks. When Wi-Fi is enabled, iOS uses a randomized MAC address so that devices cannot be tracked by anyone sniffing wireless traffic.
Two-factor authentication is an option in iOS to ensure that even if an unauthorized person knows an Apple ID and password combination, they cannot gain access to the account. It works by requiring not only the Apple ID and password, but also a verification code that is sent to a device that is already known to be trusted. If an unauthorized user attempts to sign in using another user's Apple ID, the owner of the Apple ID receives a notification that allows them to deny access to the unrecognized device.
- Clover, Juli (July 19, 2017). "Apple Releases iOS 10.3.3 With Multiple Bug Fixes and Security Updates". MacRumors.
- "New Downloads Now Available". Apple Developer. Apple Inc. July 19, 2017. Archived from the original on July 28, 2017.
- "Apple Seeds Sixth Beta of iOS 11 to Developers". Retrieved 2017-08-14.
- "New Beta Downloads Now Available - News and Updates - Apple Developer". developer.apple.com. Retrieved 2017-08-14.
- "Apple – iPad Pro – Specs". Apple. Retrieved October 24, 2015.
- "Apple – iPad mini 4 – Specs". Apple. Retrieved October 24, 2015.
- "Apple – iPad Air 2 – Technical Specifications". Apple. Retrieved October 24, 2015.
- "Apple – iPhone 6s – Technical Specifications". Apple. Retrieved October 24, 2015.
- Satariano, Adam; Burrows, Peter; Stone, Brad (October 14, 2011). "Scott Forstall, the Sorcerer's Apprentice at Apple". Bloomberg Businessweek. Bloomberg L.P. Retrieved April 1, 2017.
- Kim, Arnold (October 12, 2011). "Scott Forstall's Personality, Origins of iOS, and Lost iPhone 4 Prototype". MacRumors. Retrieved April 1, 2017.
- Thomas, Owen (January 9, 2007). "Apple: Hello, iPhone". CNN Money. CNN. Retrieved April 1, 2017.
- Eadicicco, Lisa (January 9, 2017). "Watch Steve Jobs Unveil the First iPhone 10 Years Ago Today". Time. Retrieved April 1, 2017.
- Honan, Mathew (January 9, 2007). "Apple unveils iPhone". Macworld. International Data Group. Retrieved April 1, 2017.
- Block, Ryan (January 9, 2007). "Live from Macworld 2007: Steve Jobs keynote". Engadget. AOL. Retrieved April 1, 2017.
- Wright, Mic (September 9, 2015). "The original iPhone announcement annotated: Steve Jobs’ genius meets Genius". The Next Web. Retrieved April 1, 2017.
- "iOS: A visual history". The Verge. Vox Media. September 16, 2013. Retrieved April 1, 2017.
- Gonsalves, Antone (October 11, 2007). "Apple Launches iPhone Web Apps Directory". InformationWeek. UBM plc. Retrieved April 1, 2017.
- "Jobs’ original vision for the iPhone: No third-party native apps". 9to5Mac. October 21, 2011. Retrieved April 1, 2017.
- Fletcher, Nik (October 17, 2007). "Apple: "we plan to have an iPhone SDK in developers' hands in February"". Engadget. AOL. Retrieved April 1, 2017.
- Eran Dilger, Daniel (March 7, 2017). "Nine Years of Apple's iOS SDK generated $60 billion, 1.4 million jobs". AppleInsider. Retrieved April 1, 2017.
- Elmer-DeWitt, Philip (October 17, 2007). "Steve Jobs: Apple Will Open iPhone to 3rd Party Apps in February". Fortune. Time Inc. Retrieved April 1, 2017.
- Block, Ryan (March 6, 2008). "Live from Apple's iPhone SDK press conference". Engadget. AOL. Retrieved April 1, 2017.
- Dalrymple, Jim; Snell, Jason (February 27, 2008). "Apple: iPhone SDK, enterprise announcement next week". Macworld. International Data Group. Retrieved April 1, 2017.
- Ricker, Thomas (July 10, 2008). "Jobs: App Store launching with 500 iPhone applications, 25% free". Engadget. AOL. Retrieved April 1, 2017.
- "App Store Downloads Top 100 Million Worldwide". Apple Press Info. Apple Inc. September 9, 2008. Retrieved April 1, 2017.
- Myslewski, Rik (January 16, 2009). "iPhone App Store breezes past 500 million downloads". The Register. Situation Publishing. Retrieved April 1, 2017.
- Siegler, MG (June 8, 2009). "State Of The iPhone Ecosystem: 40 Million Devices and 50,000 Apps". TechCrunch. AOL. Retrieved April 1, 2017.
- Moren, Dan (November 4, 2009). "App Store officially passes 100,000 app mark". Macworld. International Data Group. Retrieved March 29, 2017.
- Frommer, Dan (November 4, 2009). "iPhone App Store Passes 100,000 Apps". Business Insider. Axel Springer SE. Retrieved March 29, 2017.
- Brian, Matt (August 28, 2010). "Apple’s App Store Now Features 250,000 Apps". The Next Web. Retrieved March 29, 2017.
- Elmer-DeWitt, Philip (August 28, 2010). "Apple App Store: 250,000 and counting". Fortune. Time Inc. Retrieved March 29, 2017.
- Crook, Jordan (July 24, 2012). "Apple App Store Hits 650,000 Apps: 250,000 Designed For iPad, $5.5B Paid Out To Devs". TechCrunch. AOL. Retrieved March 29, 2017.
- Ingraham, Nathan (October 22, 2013). "Apple announces 1 million apps in the App Store, more than 1 billion songs played on iTunes radio". The Verge. Vox Media. Retrieved March 29, 2017.
- Fiegerman, Seth (October 22, 2013). "Apple's App Store Tops 1 Million Apps". Mashable. Retrieved March 29, 2017.
- Golson, Jordan (June 13, 2016). "Apple’s App Store now has over 2 million apps". The Verge. Vox Media. Retrieved March 29, 2017.
- Beck, Kellen (June 13, 2016). "Apple's App Store now has over 2 million apps". Mashable. Retrieved March 29, 2017.
- Carson, Erin (June 13, 2016). "Apple by the numbers: 2 million apps, 15 million Apple Music subscribers". CNET. CBS Interactive. Retrieved March 29, 2017.
- Goode, Lauren (January 5, 2017). "Apple's App Store just had the most successful month of sales ever". The Verge. Vox Media. Retrieved March 29, 2017.
- Dignan, Larry (January 5, 2017). "Apple's App Store 2016 revenue tops $28 billion mark, developers net $20 billion". ZDNet. CBS Interactive. Retrieved March 29, 2017.
- Kastrenakes, Jacob (March 21, 2016). "There are now 1 million iPad apps". The Verge. Vox Media. Retrieved April 1, 2017.
- Perez, Sarah (August 10, 2016). "App Store to reach 5 million apps by 2020, with games leading the way". TechCrunch. AOL. Retrieved March 29, 2017.
- Bangeman, Eric (September 17, 2007). "The iPod meets the iPhone: a review of the iPod touch". Ars Technica. Condé Nast. Retrieved June 21, 2017.
- Miller, Dan (January 27, 2010). "Apple announces iPad". Macworld. International Data Group. Retrieved June 21, 2017.
- Tartakoff, Joseph (June 7, 2010). "Apple Avoids iPhone-Like Trademark Battle Thanks To Cisco, FaceTime Deals". paidContent. Retrieved February 2, 2011.
- Juli Clover (October 5, 2016). "Apple's First iOS Developer Academy Opens October 6 at University of Naples". MacRumors. Retrieved December 22, 2016.
- Mike Wuerthele (October 5, 2016). "Apple's first European iOS Developer Academy opening on Thursday in Naples, Italy". AppleInsider. Retrieved December 22, 2016.
- "App Store - Support - Apple Developer". Apple Inc. Retrieved August 9, 2017.
- Caldwell, Serenity (October 15, 2011). "Up close with iOS 5: Wireless syncing and updating". Macworld. International Data Group. Retrieved June 20, 2017.
- Clover, Juli (September 13, 2016). "Apple Releases iOS 10 With Redesigned Lock Screen, New Messages Features, Third-Party Siri, and More". MacRumors. Retrieved April 1, 2017.
- Ngo, Dong (July 7, 2016). "iPhones and iPads that will -- and won't -- work with iOS 10". CNET. CBS Interactive. Retrieved April 1, 2017.
- Welch, Chris (June 5, 2017). "Apple announces iOS 11 with new features and better iPad productivity". The Verge. Vox Media. Retrieved June 6, 2017.
- "About that $20 upgrade...". CNET. CBS Interactive. January 15, 2008. Retrieved June 20, 2017.
- Dalrymple, Jim (February 7, 2008). "Accounting rules behind iPod touch update charge". Macworld. International Data Group. Retrieved June 20, 2017.
- Oliver, Sam (June 25, 2009). "Upgrade fee sees few iPod touch users updating to 3.0 software". AppleInsider. Retrieved June 20, 2017.
- Foresman, Chris (September 14, 2009). "Accounting rules change could end iPod touch update fee". Ars Technica. Condé Nast. Retrieved June 20, 2017.
- Elmer-DeWitt, Philip (September 14, 2009). "Accounting rule change in Apple’s favor". Fortune. Time Inc. Retrieved June 20, 2017.
- "Home button - Apple". help.apple.com. Retrieved May 24, 2015.
- "About iOS passcodes – Apple Support". support.apple.com. Retrieved May 24, 2015.
- "Apple's iOS 7 brings quick Spotlight search access to every app page". AppleInsider. June 10, 2013. Retrieved September 18, 2013.
- "Search on iPad with iOS 7". October 21, 2013. Retrieved March 1, 2014.
- "Hands-on with the new, proactive Spotlight in iOS 9". September 16, 2015. Retrieved October 17, 2015.
- Seifert, Dan (September 13, 2016). "iOS 10 will make you love your lock screen". The Verge. Vox Media. Retrieved April 1, 2017.
- Matthias Böhmer, Antonio Krüger. A Study on Icon Arrangement by Smartphone Users. In Proceedings of the SIGCHI Conference on Human Factors in Computing Systems (CHI '13). ACM, New York, NY, USA, 2137–2146.
- Gruber, John. "4". Daring Fireball. Retrieved July 11, 2015.
- "Fonts – Apple Developer". developer.apple.com. Retrieved September 8, 2015.
- "How to create nested folders on iOS 7". Retrieved December 20, 2013.
- "iPhone 4S – Always know what's up in Notification Center". Apple Inc. Archived from the original on February 14, 2012.
- Tanasychuk, Mike (September 15, 2016). "How to use VoiceOver on iPhone and iPad". iMore. Retrieved March 31, 2017.
- Tibken, Shara (March 25, 2016). "Seeing eye phone: Giving independence to the blind". CNET. CBS Interactive. Retrieved March 31, 2017.
- Tibken, Shara (November 3, 2016). "Apple iPhone tech helps reinvent the hearing aid". CNET. CBS Interactive. Retrieved March 31, 2017.
- Wing Kosner, Anthony (August 16, 2014). "Made For iPhone Hearing Aids: Hands On With Halo, A Mission-Critical Wearable". Forbes. Retrieved March 31, 2017.
- Aquino, Steven (June 26, 2016). "Accessibility was all around this year’s WWDC". TechCrunch. AOL. Retrieved March 31, 2017.
- Kornowski, Liat (May 2, 2012). "How the Blind Are Reinventing the iPhone". The Atlantic. Atlantic Media. Retrieved March 31, 2017.
- Aquino, Steven (May 19, 2016). "When it comes to accessibility, Apple continues to lead in awareness and innovation". TechCrunch. AOL. Retrieved March 31, 2017.
- "iOS 4 iPhone Update RELEASED: A Guide To iOS 4". The Huffington Post. June 21, 2010. Retrieved April 13, 2013.
- Albanesius, Chloe (June 21, 2010). "Apple iPhone iOS 4 Software Update Expected Monday". PC Magazine. Retrieved April 14, 2013.
- Cheng, Jacqui (June 21, 2010). "Ars reviews iOS 4: what’s new, notable, and what needs work". Ars Technica. Condé Nast. Retrieved April 1, 2017.
- Ray, Bill (November 22, 2010). "iOS 4.2 multi-tasking comes to the iPad". The Register. Retrieved April 14, 2013.
- "iOS: Understanding multitasking". Apple. Retrieved September 14, 2013.
- Newman, Jared (June 22, 2010). "Multitasking With iOS 4 is Horrible: Apple Blew It". PC World. Retrieved April 14, 2013.
- "iOS 4 walkthrough". June 14, 2010. Retrieved June 14, 2010.
- "Apple announces multitasking for iPhone OS 4 (iPhone 3GS/iPod touch G3 only)". April 8, 2010. Retrieved June 14, 2010.
- "iOS Application Programming Guide – Background Execution". Developer.apple.com. Retrieved September 4, 2015.
- Yoni Heisler (June 12, 2013). "Jon Rubinstein: OS X and iOS 7 borrow features from webOS". Retrieved September 23, 2013.
- Prabhu, Gautam. "iOS 9 vs. iOS 8: A look at the UI changes in iOS 9". iPhone Hacks. Retrieved September 20, 2015.
- "iOS: Force an app to close". Apple Inc. Retrieved October 9, 2012.
- "iOS 7 multitasking". Tuaw. September 18, 2013. Retrieved March 21, 2014.
- Snell, Jason (April 8, 2010). "Inside iPhone 4.0's multitasking". Macworld. Retrieved April 14, 2013.
- German, Kent (June 23, 2010). "Apple iPhone 4 AT&T review". CNET. CBS Interactive. Retrieved April 1, 2017.
- Hollington, Jesse (June 21, 2010). "Instant Expert: Secrets & Features of iOS 4". iLounge. Retrieved April 14, 2013.
- Schonfeld, Erick (February 4, 2010). "Siri's IPhone App Puts A Personal Assistant In Your Pocket". TechCrunch. AOL. Retrieved June 21, 2017.
- Wortham, Jenna (April 29, 2010). "Apple Buys a Start-Up for Its Voice Technology". The New York Times. Retrieved June 21, 2017.
- Marsal, Katie (April 28, 2010). "Apple acquires Siri, developer of personal assistant app for iPhone". AppleInsider. Retrieved June 21, 2017.
- Rao, Leena (April 28, 2010). "Confirmed: Apple Buys Virtual Personal Assistant Startup Siri". TechCrunch. AOL. Retrieved June 21, 2017.
- Golson, Jordan (October 4, 2011). "Siri Voice Recognition Arrives On the iPhone 4S". MacRumors. Retrieved June 21, 2017.
- Velazco, Chris (October 4, 2011). "Apple Reveals Siri Voice Interface: The “Intelligent Assistant” Only For iPhone 4S". TechCrunch. AOL. Retrieved June 21, 2017.
- Kumparak, Greg (October 4, 2011). "The Original Siri App Gets Pulled From The App Store, Servers To Be Killed". TechCrunch. AOL. Retrieved June 21, 2017.
- Purewal, Sarah Jacobsson; Cipriani, Jason (February 16, 2017). "The complete list of Siri commands". CNET. CBS Interactive. Retrieved June 21, 2017.
- Sumra, Husain (June 13, 2016). "Apple Opens Siri to Third-Party Developers With iOS 10". MacRumors. Retrieved June 21, 2017.
- Olivarez-Giles, Nathan (June 13, 2016). "Apple iOS 10 Opens Up Siri and Messages, Updates Music, Photos and More". The Wall Street Journal. Dow Jones & Company. Retrieved June 21, 2017. (subscription required)
- Matney, Lucas (June 5, 2017). "Siri gets language translation and a more human voice". TechCrunch. AOL. Retrieved June 21, 2017.
- Gartenberg, Chaim (June 5, 2017). "Siri on iOS 11 gets improved speech and can suggest actions based on how you use it". The Verge. Vox Media. Retrieved June 21, 2017.
- "What's New in iOS 4". Apple. Retrieved June 14, 2010.
- "Apple's Game Center debuts next week – Game Hunters: In search of video games and interactive awesomeness". USA Today. January 9, 2010. Retrieved September 1, 2010.
- Holt, Chris. "iOS 4.1's GameCenter to Hit iPhone Next Week – PCWorld Business Center". Pcworld.com. Retrieved September 1, 2010.
- "iOS 4.2 Software Update for iPad". Apple Inc. Retrieved October 9, 2012.
- "Game Center". Apple. Sep 2010. Retrieved September 7, 2010.
- Wollman, Dana (September 10, 2013). "iOS 7 will be 64-bit, just like the iPhone 5s' new A7 chip". Engadget.
- Souppouris, Aaron (September 12, 2013). "Why Apple's 64-bit iPhone chip is a bigger deal than you think". The Verge.
- Cunningham, Andrew (July 2, 2015). "The state of the 64-bit transition in iOS, and what's left to be done". Ars Technica.
- Cunningham, Andrew (June 5, 2017). "iOS 11 drops the iPhone 5 and 5C and the fourth-gen iPad". Ars Technica.
- Mayo, Benjamin (June 6, 2017). "32-bit apps will not launch on iOS 11, Mac App Store transition to 64-bit from 2018". 9to5Mac.
- Cunningham, Andrew (April 13, 2017). "What the death of 32-bit iOS could mean for Apple’s hardware and software". Ars Technica.
- "Jobs’ original vision for the iPhone: No third-party native apps". 9to5Mac. October 21, 2011. Retrieved June 21, 2017.
- Duncan, Geoff (October 17, 2007). "Apple confirms iPhone SDK coming next year". Digital Trends. Retrieved June 21, 2017.
- "Steve Jobs confirms native iPhone SDK by February". AppleInsider. October 17, 2007. Retrieved June 21, 2017.
- Dalrymple, Jim (March 6, 2008). "Apple unveils iPhone SDK". Macworld. International Data Group. Retrieved June 21, 2017.
- Block, Ryan (March 6, 2008). "Live from Apple's iPhone SDK press conference". Engadget. AOL. Retrieved June 21, 2017.
- Guevin, Jennifer (March 6, 2008). "FAQ: What does the iPhone SDK mean?". CNET. CBS Interactive. Retrieved June 21, 2017.
- Kim, Arnold (March 6, 2008). "Apple Releases iPhone SDK, Demos Spore, Instant Messaging". MacRumors. Retrieved June 21, 2017.
- Mayo, Benjamin (September 11, 2015). "Apple now allowing developers to submit iOS 9, OS X El Capitan and native Watch apps to the App Store". 9to5Mac. Retrieved June 21, 2017.
- Sande, Steven (June 10, 2013). "New iOS SDK features for developers". Engadget. AOL. Retrieved June 21, 2017.
- Sinicki, Adam (June 9, 2016). "Developing for Android vs developing for iOS – in 5 rounds". Android Authority. Retrieved June 21, 2017.
- Paul, Ryan (September 15, 2009). "MonoTouch drops .NET into Apple’s walled app garden". Ars Technica. Condé Nast. Retrieved June 21, 2017.
- Dove, Jackie (April 11, 2010). "Adobe unleashes Creative Suite 5". Macworld. International Data Group. Retrieved June 21, 2017.
- "StatCounter Global Stats - Browser, OS, Search Engine including Mobile Usage Share". statcounter.com. Retrieved February 19, 2017.
- "iOS leapfrogs Android with 410 million devices sold and 650,000 apps". InsideMobileApps. July 24, 2012. Retrieved July 24, 2012.
- Ingraham, Nathan (June 2, 2014). "Apple has sold more than 800 million iOS devices, 130 million new iOS users in the last year". The Verge. Vox Media. Retrieved April 1, 2017.
- Rossignol, Joe (January 27, 2015). "Tim Cook: Apple Has Sold More Than 1 Billion iOS Devices". MacRumors. Retrieved June 21, 2017.
- Kahn, Jordan (January 27, 2015). "Apple announces 1 billion iOS devices sold". 9to5Mac. Retrieved June 21, 2017.
- Saylor, Michael (2012). The Mobile Wave: How Mobile Intelligence Will Change Everything. Vanguard Press. p. 33. ISBN 1-59315-720-7.
- "Android and iOS Squeeze the Competition, Swelling to 96.3% of the Smartphone Operating System Market for Both 4Q14 and CY14, According to IDC" (Press release). IDC. February 24, 2015. Archived from the original on February 25, 2015.
- "Worldwide Tablet Growth Hits the Brakes, Slowing to the Low Single Digits in the Years Ahead, According to IDC" (Press release). IDC. March 12, 2015. Archived from the original on March 13, 2015.
- "StatCounter Global Stats: Top 7 Mobile Operating Systems on Feb 2015". Retrieved March 6, 2015.
- Sui, Linda (November 2, 2016). "Strategy Analytics: Android Captures Record 88 Percent Share of Global Smartphone Shipments in Q3 2016". Strategy Analytics. Retrieved November 27, 2016.
- Rossignol, Joe (November 2, 2016). "iOS Adoption Remains at Lowest Levels Since 2014 as Android Captures Record 87.5% Market Share". MacRumors. Retrieved November 27, 2016.
- Ricker, Thomas (July 10, 2007). "iPhone Hackers: "we have owned the filesystem"". Engadget. AOL. Retrieved April 1, 2017.
- Healey, Jon (August 6, 2007). "Hacking the iPhone". Los Angeles Times. Retrieved August 6, 2007.
- "Apple's Joswiak: We Don't Hate iPhone Coders". September 11, 2007. Retrieved February 19, 2017.
- Baig, Edward C. (June 26, 2007). "Apple's iPhone isn't perfect, but it's worthy of the hype". USA Today. Retrieved June 28, 2007.
- IPad, MAX (May 6, 2010). "Jailbreaking Explained". IPad Forums. Retrieved November 4, 2012.
- Kravets, David (July 26, 2010). "U.S. Declares iPhone Jailbreaking Legal, Over Apple's Objections". Wired. Retrieved December 13, 2011.
- "U.S. Copyright Office Final 2010 Anti-Circumvention Rulemaking" (PDF). U.S. Copyright Office. July 27, 2010. Retrieved August 21, 2012.
- Mobile, Know Your (May 19, 2010). "Locked / Unlocked – a definition of the terms Locked and Unlocked from the Know Your Mobile mobile phone glossary". Know Your Mobile. Retrieved November 4, 2012.
- "AT&T – What are the eligibility requirements for unlocking iPhone?". AT&T. Retrieved August 21, 2012.
- "iPhone: About unlocking". Apple Inc. Website. May 22, 2012. Retrieved August 21, 2012.
- "iPhone: Wireless Carrier Support and Features". Apple Inc. Website. April 12, 2013. Retrieved May 13, 2013.
- "How to unlock your AT&T iPhone". USA Today. April 9, 2012. Retrieved August 21, 2012.
- "Unauthorized modification of iOS can cause security vulnerabilities, instability, shortened battery life, and other issues". Apple Inc. Website. February 9, 2013. Retrieved May 13, 2013.
- "iPad DRM endangers our rights".
- Anderson, Nate (January 27, 2010). "Protestors: iPad is nothing more than a golden calf of DRM". Ars Technica. Condé Nast. Retrieved April 1, 2017.
- "Mobile Devices and the Next Computing Revolution". February 3, 2010. Retrieved June 9, 2010.
- Bobbie Johnson (February 1, 2010). "Apple iPad will choke innovation, say open internet advocates". The Guardian. Retrieved February 7, 2010.
- "Microsoft PR spokesman condemns iPad for being "locked down"".
- "Apple's Trend Away From Tinkering". Slashdot. January 31, 2010. Retrieved June 9, 2010.
- Steve Wozniak (Interviewee) (January 22, 2011). Campus Party Brasil 2011 – Geek Pride e Wozniak. Fragoso, Victor. Retrieved March 7, 2011.
- Leander Kahney (January 30, 2010). "Pundits On The iPad's Closed System: It's Doom For PCs, No It's Great". Retrieved June 9, 2010.
- Available in iOS 5 to iOS 7 via General > About > Diagnostics & Usage > Diagnostics & Usage Data >(date and time).panic.plist, after a kernel crash
Available in iOS 8 to iOS 10 via Privacy > Diagnostics & Usage > Diagnostics & Usage Data > JetsamEvent-(date and time).ips, when low in memory
- Apple Inc. (May 2016). "iOS Security Guide" (PDF). apple.com.
- "ASLR - The iPhone Wiki". www.theiphonewiki.com. Retrieved December 6, 2016.
- "iOS Keychain Services Tasks". developer.apple.com. Retrieved December 6, 2016.
- "Two-factor authentication for Apple ID". Apple Support. Retrieved December 6, 2016.
- Apple Inc., Apple press release library, Retrieved September 19, 2007.
- Mactracker (mactracker.ca), Apple Inc. model database, version as of 26 July 2007.
- Hillegass, Aaron; Conway, Jon (March 22, 2012). iOS Programming: The Big Nerd Ranch Guide (3rd ed.). Pearson. p. 590. ISBN 978-0-321-82152-2.
- Turner, Kirby (December 19, 2011). Learning iPad Programming: A Hands-on Guide to Building iPad Apps with iOS 5 (1st ed.). Pearson. p. 816. ISBN 978-0-321-75040-2.
- Mark, Dave; LaMarche, Jeff (July 21, 2009). Beginning iPhone 3 Development: Exploring the iPhone SDK (1st ed.). Apress. p. 584. ISBN 1-4302-2459-2.
- Mark, Dave; LaMarche, Jeff (December 29, 2009). More iPhone 3 Development: Tackling iPhone SDK 3 (1st ed.). Apress. p. 552. ISBN 1-4302-2505-X.