DECEMBER 2006

Code: C-13                                                                               Subject: OPERATING SYSTEMS

Time: 3 Hours                                                                                                     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. When two or more processes are waiting indefinitely for an event which can be solved by one of the waiting processes, the state is called as

(A)  Hanging                                        (B)  Deadlock

(C)   Starvation                                    (D)  Circular wait

             b.   One solution to external fragmentation is 

(A) Swapping                                     (B)  Garbage collection

(C) Compaction                                  (D)  Paging           

             c.   Demand paging technique is used in 

(A) Virtual memory                             (B)  Cache memory

(C)  Physical memory                          (D)  Secondary memory

             d.   Batch processing operating systems refer to their resident code as

(A)  Dispatcher                                    (B)  Scheduler

(C)  Linker                                          (D)  Supervisor

             e.   For a segment with base = 400 and Length = 350, the physical address for a logical address 575 is 

(A)  975, valid                                     (B)  750, invalid

(C)  750, valid                                     (D)  975, invalid

             f.   ‘Fork’ is a

(A) System call                                    (B) User process

                   (C) Kernel process                              (D) I/O process

     g.   The operating system with bounded delays is a 

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

                   (C) Distributed system                         (D)  Time sharing system

             h.   The type of network suited for a university campus is a

(A) WAN                                           (B)  MAN

                   (C) LAN                                             (D)  INTERNETWORK

i.    ‘Signal’ and ‘wait’ are two procedures belonging to   

(A) Semaphores                                  (B)  Queues

                   (C) Monitors                                       (D)  Mailboxes

             j.    Command interpretation is done by

(A) Kernel                                           (B)  Shell

                   (C) Microkernel                                  (D)  Supervisor     

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

Q.2     a.   Explain the three main purposes of an operating system?                                     (4)

b.   What are the differences between a trap and an interrupt? What is the use of each function?                        (6)

             c.   What is layered approach to OS design? Describe its advantages and disadvantages.                      (6)

Q.3     a.   Describe any two methods of inter process communication.                                (8)

             b.   What are the benefits of multithreaded programming?                                          (4)

c.   Explain thread creation in Java.                                                                          (4)

Q.4     a.   What is main goal of a scheduling algorithm in a Real time operating system?  Describe any one such algorithm.                                            (4)

b.   What is the advantage of having different time-quantum sizes on different levels of multilevel queuing system?                                                                                                                         (4)

             c.   What is ‘Mutual Exclusion’?  Write pseudo code to implement mutual exclusion using

(i) Test and Set instruction and

(ii) Swap instruction                                                                        (8)

Q.5     a.   What is a Resource allocation graph? What is its role in solving deadlock situations?                       (6)

             b.   Draw the resource allocation graph for the following situation and determine if the system is in deadlock:

                   Given the sets P, R and E as

(4)

             c.   Not every unsafe state leads to a deadlock. Give an example to show that the processes in an unsafe state complete their execution without entering a deadlock state.                                                 (6)

  Q.6     a.   Consider the following segment table:  

Segment	Base	Length
0	219	600
1	2300	14
2	90	100
3	1327	580
4	1952	96

                   What are the physical addresses for the following logical addresses?  How many of these are invalid?         

                   (i)    0430                                            (ii)    110

                   (iii)  2500                                            (iv)   3400

                   (v)   4112                                            (vi)   128

                   (vii) 235                                              (viii) 3679                                               (8)

             b.   Describe with a diagram the paging hardware with TLB.                                     (8)

Q.7     a.   Describe in brief any eight operations carried out on files.                                    (8)

             b.   Describe with a diagram the UNIX STREAMS structure.                                   (8)

Q.8     a.   Suppose that a disk drive has 5000 cylinders, numbered 0 to 4999.  The drive is currently serving a request at cylinder 143, and the previous request was at cylinder 125.  The queue of pending requests, in FIFO order, is

86, 1470, 913, 1774, 948, 1509, 1022, 1750, 130.

                   Starting from the current head position, what is the total head distance (in cylinders) that the disk arm moves to satisfy all pending requests for each of the following disk scheduling algorithms?

                   FCFS, SSTF, SCAN, LOOK, C-SCAN, C-LOOK.                                     (12)

b. What are the benefits of a distributed file system when compared to a file system in a centralized system?                                                               (4)

Q.9     a.   Explain the Bully algorithm.                                                                                (6)

b.   What are the main differences between capability lists and access lists?               (4)

c. With respect to Window 2000 operation system explain the following:

(i) Page table structure.

(ii) Packet driven I/O system.  (6)