What are preemtive and cooperative multitasking and when was it introduced? How does Mac OS X compare to Mac OS 9 in this regard? What other operating systems use either preemtive or cooperative multitasking?

There are two basic types of multitasking: preemptive and cooperative.

preemptive – preemptive multitasking, the operating system parcels out CPU time slices to each program (introduced with Mac OS X 10.0)

cooperative multitasking – each program can control the CPU for as long as it needs it. (Previous operating systems (Mac OS 9))

Other OSes

OS/2, Windows 95, Windows NT, the Amiga operating system and UNIX use preemptive multitasking, whereas Microsoft Windows 3.x and the MultiFinder (for Macintosh computers) used cooperative multitasking.