Code: C-13                                                                               Subject: OPERATING SYSTEMS

Time: 3 Hours                                                   June 2006                                                   Max. Marks: 100

NOTE: There are 9 Questions in all.

· Question 1 is compulsory and carries 20 marks. Answer to Q. 1. must be written in the space provided for it in the answer book supplied and nowhere else.

· Out of the remaining EIGHT Questions answer any FIVE Questions. Each question carries 16 marks.

· Any required data not explicitly given, may be suitably assumed and stated.

Q.1       Choose the correct or best alternative in the following:                                         (2x10)

a. The operating system with bounded delays is a

(A)  Hard real time system                   (B)  Soft real time system

(C)   Distributed system                       (D)  Time sharing system

             b.   Execution of an Interrupt handler routine is an

(A) I/O process                                  (B)  Kernel process

(C)  User process                                (D)  Memory process        

             c.   The command line interpreter program is also called as 

(A) kernel                                           (B)  process

(C)  protocol                                       (D)  shell

             d.   ‘Fork’ is a

(A)  user process                                 (B)  CPU bound process

(C)  System call                                   (D)  I/O operation

             e.   Special software used to create a Job queue is called a

(A)  editor                                           (B)  interpreter

(C)  driver                                           (D)  spooler

             f.   In terms of average wait time the optimum scheduling algorithm is

(A) FCFS                                           (B) SJF

                   (C) Priority                                          (D) RR

     g.   Bakery algorithm is one of the solutions to

(A) Scheduling                                     (B)  Inter process communication

                   (C) Process synchronisation                 (D)  Deadlock

             h.   Presence of Loops / cycles in a Resource Allocation Graph indicates

(A) Deadlock state                              (B)  Safe state

                   (C) Unsafe state                                  (D)  Wait state

             i.    The memory management system that supports user’s view of memory is

(A) Segmentation                                 (B)  Paging

                   (C) Virtual memory                              (D)  Contiguous memory

             j.    Files with an extension .bin is an

(A) archive file                                     (B)  multimedia file

                   (C) object file                                      (D)  executable file

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

Q.2     a.   Define one essential feature of the following operating systems:-

(i)     Batch                                          (ii)   Interactive

                   (iii)   Time sharing                                (iv)  Real time

                   (v)    Network                                     (vi)  Parallel

                   (vii)  Distributed                                   (viii)Handheld                                         (8)

b.   Distinguish between ‘user mode’ and ‘privileged mode’ of a CPU.                      (4)          

             c.   Which of the following instructions are in user mode and which are in privileged mode?

                   (i)  Set value of a timer                         (ii)  Clear memory

                   (iii)Turn off interrupts                           (iv) Switch from user mode to             

                                                                                     privileged mode.                               (4)

Q.3     a.   What is the purpose of a command interpreter program?  Why is it usually separate from a kernel?                                                            (4)

             b.   Explain the following:

(i)   Context switch.                             (ii)  Process state.

                   (iii) Interrupt.                                       (iv) CPU-I/O burst cycle.                        (8)

c.   Differentiate between user threads and kernel threads. Give examples for each.                   (4)

Q.4     a.   What is dispatch latency?  How does it affect Real time scheduling?  Suggest some solutions to keep dispatch latency low.                            (10)

             b.   Consider the following set of processes.

Process Burst time (ms)

   --------                                        10                                                              

   --------                                       29

   -------- 3

   --------                                       7                                                                

   --------                                       12

                   Evaluate the performance of FCFS, SJF and RR (Quantum = 10 ms) algorithms for scheduling the above processes.                                           (6)

Q.5     a.   With simple data structures / procedures, explain the following problems of synchronisation:

(i) Bounded Buffer problem.

(ii) Readers –  writers problem.

(iii) Dining philosophers problem.                                                   (12)

             b.   Construct a Resource Allocation Graph for the following situation.  Check if the system is in deadlock state:

                   The sets of process are

                   Edges are

                   Set of Resources  with 2 instances each of  and .               (4)

  Q.6     a.   Describe the problems and solutions to contiguous memory allocation.  Assume fixed sized partitions.                                                                    (8)

             b.   Given memory partitions of 100 KB, 500 KB, 200 KB, 300 KB and 600 KB (in order), how would each of the first fit, best fit and worst fit algorithms place processes of 212 KB, 417 KB, 112 KB and 426 KB (in order)?  Which algorithm makes the most efficient use of memory?                      (8)

Q.7     a.   Describe General Graph Directory and Acrylic Graph Directory structures.         (6)

             b.   Compare linked and indexed methods of file allocation.                                       (4)

             c.   Describe the deadlock-detection algorithm in a fully distributed system.               (6)

Q.8     a.   Describe the steps in an interrupt driver I/O cycle.                                              (6)

b. Comment on the performance of a tertiary storage system in terms of speed, reliability and cost.                                                                 (6)

             c.   List the advantages of RAID structures.                                                              (4)

Q.9     a.   Describe with a neat flow diagram, the ISO protocol layer.                                 (8)

b.   What is cryptography?  Explain authentication and encryption.  Compare them.                  (8)