Consider three processes, all arriving at time zero, with total execution time of $$10,20,$$ and $$30$$ units, respectively. Each process spends the first $$20$$% of execution time doing $${\rm I}/O$$, the next $$70$$% of time doing computation, and the last $$10$$% of time doing $${\rm I}/O$$ again. The operating system uses a shortest remaining compute time first scheduling algorithm and scheduling a new process either when the running processes gets blocked on $${\rm I}/O$$ or when the running process finishes its compute burst. Assume that all $${\rm I}/O$$ operations can be overlapped as much as possible. For what percentage of time does the $$CPU$$ remain idle?

Consider the following code fragment:

if (fork() == 0)
{
   a = a + 5;
   printf("%d, %d \n", a, &a);
}
else
{
   a = a - 5;
   printf ("%d, %d \n", a, &a);
}

Let $$u,v$$ be the values printed by the parent process, and $$x,y$$ be the values printed by the child process. Which one of the following is TRUE?

Consider the following set of processes, with the arrival times and the $$CPU$$-burst times given in milliseconds.

What is the average turnaround time for these processes with the preemptive shortest remaining processing time first $$(SRTF)$$ algorithm?

A uni-processor computer system only has two processes, both of which alternate $$10$$ $$ms$$ $$CPU$$ bursts with $$90$$ $$ms$$ $${\rm I}/O$$ bursts. Both the processes were created at nearly the same time. The $${\rm I}/O$$ of both processes can proceed in parallel. Which of the following scheduling strategies will result in the least $$CPU$$ utilization (over a long period of time) for this system?