OS's (Score 1)

When it comes down to it, an operating system is just a software layer designed to allow programs to interface with a computers hardware. They've grown immensely from DOS right up to Vista, from using basic interrupts to full-blown multitaking/threaded beasts like Vista...from providing minimal graphics capabities (who ever used an interrupt to draw a pixel? lol) to providing a complete graphics windowing system. The iPhone does use OSX, in that programs for the iPhone can use most of the same function calls, parameters, handles, etc as they would if they were on OSX (PPC) or OSX (Intel). They still have to be compiled for the appropriate processor however.