Test I
Operating Systems and Networking
CS-330
Fall 2006
Time: 2:00 hrs.
Answer any five questions from below
Policy: Open books and open notes
Date: September 27, 2006
1. State three major objectives that an Operating Systems module attempts to
accomplish in a modern multi-user, multi-tasking computing systems.
Rationalize your answer.
2. What is cycle stealing in DMA set up? What cycle are we referring to? When the
bus is captured by the DMA module for data transfer, it is possible that CPU
sometimes may need the bus to access the memory. How would it be handled by
the system?
3. One approach to handling multiple interrupts is to ignore them altogether by
disabling further interrupts while the current interrupt is being handled. How well
would it work? What would be its problems, if any?
4. Why fairness is a serious issue in process scheduling? Is fairness principle
abandoned in time-sharing round robin system where each participating job gets
the same time-slice? Is fairness still valid as an objective in FCFS
multiprogramming system? State your reasons.
5. What are the process states in a 5-state model? Suppose we add “Suspended state”
in it. How does a job exit from a suspended state? To speed up the entire process,
a suggestion is made that jobs “under certain conditions” may be allowed to
proceed directly to the running state from a suspended state when released.
Comment on this design.
6. Suppose a ready job (that’s a job waiting for CPU in the CPU queue) is indicated
by three-component vector associated with the job: (Job ID, CPU time needed,
and time it arrived at the CPU queue). Given, (A, 1, 0), (B, 3, 2), (C, 4, 2), (D, 5,
3) and (E, 3, 3), find the schedule time and average waiting time per job under
each discipline:
a. FCFS
b. RR with a time slice of
2
7. What is the objective(s) of a short-term scheduler? In what way does it differ from
that of a medium-term scheduler? What is more likely to be costlier if the
