How is multitasking performed in operating systems?

How is process-based multitasking achieved by u开发者_运维问答sing multi-threading in each process?

For example, consider when an operating system is running with two background process. Each process supports internally multi-threading features. Now, how does time slicing happen between and inside these processes, and how does time slicing happen between threads?

Look at publications by this man: http://en.wikipedia.org/wiki/Andrew_S._Tanenbaum

Or just feed your query into Google. There's many ways to skin the multi-tasking/multi-threading cat.

Come back when you have at least tried to find your own answers and ask some more specific questions.

One possible implementation is that the OS just schedules threads. When it switches to a thread, it obviously switches in the address space of the process the thread belongs to, but from a scheduling viewpoint the process is pretty much ignored (e.g., Windows works this way).