User interface of iPhone OS

The user interface of iPhone OS is based on the concept of direct manipulation, using multi-touch gestures. Interface control elements consist of sliders, switches, and buttons. The response to user input is supposed to be immediate to provide a fluid interface. Interaction with the OS includes gestures such as swiping, tapping, pinching, and reverse pinching. 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).
A home screen (rendered by "SpringBoard") with application icons, and a dock at the bottom of the screen, showing icons for the applications the user accesses the most, is presented when the device is turned on or whenever the home button is pressed. 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. There is no concept of starting or quitting applications, only opening an application from the home screen, and leaving the application to return to the home screen. It is possible to force an application to quit by holding down the power button until the "slide to power off" slider appears, and then holding the home button down, however. While some multitasking is permitted it is not obtrusive or obvious. However, it is limited to Apple's own applications, a limitation that will be lifted with the introduction of OS 4.0. Third-party applications are quit when left, but from the 3.0 software update, notifications can be pushed from Apple's servers to the iPhone or iPod Touch. Many of the included applications were designed to work together; allowing for the sharing or cross-propagation of data from one application to another (e.g., a phone number can be selected from an email and saved as a contact or dialed for a phone call.) The iPad includes a similar interface, except that the dock is "3D" and the background is interchangeable.

http://en.wikipedia.org/wiki/IPhone_OS
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