System calls are usually invoked by using:

Consider $$n$$ processes sharing the $$CPU$$ in a round-robin fashion. Assuming that each process switch takes $$s$$ seconds, what must be the quantum size $$q$$ such that the overhead resulting from process switching is minimized but, at the same time each process is guaranteed to get its turn at the $$CPU$$ at least every $$t$$ seconds?

Which of the following is an example of spooled device?

The process state transition diagram in Figure is representative of