Which of the following operating system is used on mobile phones ?

CONCEPT: Operating systems are designed around a target device market and an interaction model, and that design target is what places a system in the desktop class or in the handheld class. A system built for handheld phones is organised around a small touchscreen, battery-first power management, and an integrated telephony and radio stack for calls and cellular data. A system built for personal computers is organised around a large display, a windowed shell, and keyboard-and-mouse input, with no telephony layer of its own. Classifying a named system therefore means asking which device market it was designed and shipped for.

APPLICATION: Applying that test to the systems listed here, Android is the one designed and shipped for handheld phones. Released by Google in 2008, it is built on a Linux kernel, presents a touch-driven interface, and carries the telephony and radio layers a phone needs to place calls and attach to a cellular network. Handset manufacturers ship it as the operating system installed on their phones.

CONTRAST: The other systems named were designed and sold for a different device market.

• Windows Vista (Microsoft, 2007) is a Windows NT-family operating system designed and sold for personal computers, with the Aero windowed shell, keyboard-and-mouse input, and no telephony stack of its own.

• Windows XP (Microsoft, 2001) is likewise a Windows NT-family operating system designed and sold for personal computers; Microsoft's handheld phone line in that era was the separate Windows Mobile / Windows CE family, not XP.

• Because two of the three named systems were designed for personal computers rather than for phones, a choice asserting that every listed system belongs to the handheld class cannot hold.

RESULT: Among the systems listed, the operating system used on mobile phones is Android.