Normally user programs are prevented from handling $${\rm I}/O$$ directly by $${\rm I}/O$$ instructions in the for $$CPU$$ having explicit $${\rm I}/O$$ instructions, such $${\rm I}/O$$ protection is ensured by having the $${\rm I}/O$$ instructions privilege in $$CPU$$ with memory mapped $${\rm I}/O$$ there is no explicit $${\rm I}/O$$ instruction. Which one of the following is true for a $$CPU$$ with memory mapped $${\rm I}/O$$?

Consider an operating system capable of loading and executing a single sequential user process at a time. The disk head scheduling algorithm used is First Come First Served $$(FCFS).$$ If $$FCFS$$ is replaced by Shortest Seek Time First $$(SSTF),$$ claimed by the vendor to give $$50\% $$ better benchmark results, what is the expected improvement in the $${\rm I}/O$$ performance of user programs?

Using a larger block size in a fixed block size file system leads to

Which of the following requires a device driver?