Apple's operating system for mobile devices, such as the iPhone, iPod touch, iPad and Apple TV (2nd generation) devices. It shares a lot with macOS, but is optimized for touch-based interfaces.

Apple's operating system for mobile devices.

It is a derivative of Apple's desktop operating system, with which it shares many (but not all) common frameworks and other components, such as Cocoa Touch (the counterpart of the desktop framework Cocoa), the Mach/Darwin/XNU kernel and code from the Berkeley Software Distribution (BSD). Applications for iOS are written for the framework (as opposed to Mac OS X's framework) using the same IDE for official use (i. e. for submitting applications to Apple's AppStore) or using unofficial (mostly command-line only) toolchains for various operating systems (including Linux) for unofficial/jailbroken development. Mac OS is based on the foundation, itself based on several descendants.

Each iOS application runs in its own security to prevent (accidentally or intentionally) altering other applications, the operating system, or any other data. It is optimized for the CPU, GPU, power, and memory constraints of mobile devices.

The user interface of is based on the concept of direct manipulation, using multi-touch gestures. Interface control elements consist of sliders, switches, and buttons, all included in Apple's framework. 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 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).

Apple initially adapted features from Mac OS X to create iOS, but that cycle is now bidirectional. Many features on Mac OS X v10.7 were implemented first in iOS, including strict application sandboxing, an (and the implied widespread third party app code signing), and the content-centric ("natural") scrolling direction, along with AV Foundation, Core Location, and a few other frameworks.

Use the tag for questions about Cisco's IOS operating system for Cisco network routers.