Code: C-13                                                                               Subject: OPERATING SYSTEMS

Time: 3 Hours                                                                                                     Max. Marks: 100

NOTE: There are 11 Questions in all.

· Question 1 is compulsory and carries 16 marks. Answer to Q.1 A. must be written in the space provided for it in the answer book supplied and nowhere else.

· Answer any THREE Questions each from Part I and Part II. Each of these questions carries 14 marks.

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

Q.1 A.        Choose the correct or best alternative in the following:                       (2x6)

a. Distributed systems provide

(A)  Resource sharing.                         (B)  Speed.

(C)   Reliability.                                    (D)  All of these.

             b.   Naming is a method of

(A) IPC.                                             (B)  Paging.

(C)  Synchronisation.                           (D)  File management.       

             c.   Round Robin scheduling is used in

(A) Disk scheduling.                           (B)  CPU scheduling

(C)  I/O scheduling.                             (D)  Multitasking.

             d.   Banker’s algorithm is used in

(A)  Threads.                                       (B)  CPU scheduling.

(C)  Deadlock avoidance.                    (D)  Paging.

             e.   Compaction is a solution to

(A) Dead locks.                                   (B)  Fragmentation.

                   (C) Security problems.                         (D)  concurrency problems.

             f.   Page sizes in paging system are expressed in

(A) Powers of 10                                (B) Powers of 8

                   (C) Powers of 16                                (D) Powers of 2

     B. State True or False.                                                                                                                                                                                                                      (2x2)

             g.   Context switching times are dependent on Hardware.

FALSE

TRUE

             h.   All unsafe states are deadlock states.

TRUE

FALSE

PART I

Answer any THREE Questions. Each question carries 14 marks.

Q.2           List the 7 main components of the operating system and their services.              (14)

Q.3     a.   How are system calls classified?  Give examples.                                                (8)

             b.   Explain Multiprocessors and Multicomputers.                                                     (6)

Q.4     a.   Explain process scheduling with the help of a diagram.                                        (6)

             b.   With an example, discuss the preemptive SJF scheduling algorithm.                     (8)

Q.5           Compute the Average waiting time and Turn around time for the following set of processes by applying FCFS, preemptive SJF algorithms.       (14)

Process	Arrival Time (ms)	CPU burst (ms)
	0	10
	1	29
	2	3
	3	7
	4	12

  Q.6     a.   What is critical section problem?  Write an algorithmic implementation of critical section problem with two processes.                                           (10)

             b.   Describe the steps involved in Booting. (4)

PART II

Answer any THREE Questions. Each question carries 14 marks.

Q.7     a.   Define Binary Semaphores.  How is Mutual Exclusion implemented using semaphores?                   (8)

             b.   Explain bounded buffer problem of IPC.                                                             (6)

Q.8     a.   With an example, explain multiple partitioned, contiguous memory allocation.  What are the drawbacks of this method?                                        (10)

b. Define

(i) Starvation.

(ii) Thrashing.                                                                                        (4)

Q.9     a.   Given memory partitions of 100K, 500K, 200K, 300K and 600K (in order), how would each of the first-fit, best-fit and worst-fit algorithms place processes of 212K, 417K, 112K and 426K (in order)?  Which algorithm makes the most efficient use of memory?                                              (6)

b.   Explain with an example, LRU page replacement algorithm.                                (8)

Q.10     a. Describe methods used to manage free disk space in a computer system.                                                (8)

     b.   With a neat diagram, explain a typical PC Bus structure.                                     (6)

Q.11     a. Differentiate between Blocking and Non Blocking I/O.        (4)

b.   With a neat diagram, describe the steps used to transform an I/O request to Hardware Operation.                                                             (10)