The iPhone Operating System (OS) is the operating system developed by Apple Inc. for the iPhone and iPod Touch. It uses the Darwin foundation which is like the Mac OS. The iPhone OS has four layers which includes the Core OS layer, the Core Services layer, the Media layer, and the Cocoa Touch layer. The operating system takes less than half a gigabyte (GB) of the device's total memory storage.
The first beta version of the iPhone Software Development Kit (SDK) was released in March, 2008. The Apple iPhone has more than 25,000 available applications and the Apple App Store has had more than 1 billion downloads.
The interface for the iPhone operating system is based on using multi-touch gestures for direct manipulation. The interface controls consist of switches, slides, and buttons. The input from the user results in an immediate response which results in a fluid interface. Users interact with the OS includes tapping, swiping, pinching and reverse pinching. Using internal accelerometers the iPhone can be rotated on its y-axis and alters the orientation of the screen with some applications.