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B.Tech. DEGREE EXAMINATION.

Fourth Semester

Information Technology

IF 253 — OPERATING SYSTEMS

Time : Three hours Maximum : 100 marks

Answer ALL questions.

PART A — (10 ´ 2 = 20 marks)

What is meant by thrashing?

Explain the difference between logical address and physical address space.

What is the purpose of system calls?

Explain the difference between symmetric and asymmetric multiprocessing.

The ratio between the main memory cycle time and cache memor y time is 8 : 1.

Calculate the effective memory cycle time for a system who cache miss ratio is 6%.

What is a Time sharing system?

What is a Context switch?

What is dynamic loading and dynamic linking?

Define the essential properties of real time Operating System.

What are the advantages of having an inverted page table?

PART B — (5 ´ 16 = 80 marks)

(i) Discuss the critical section problem with one example. (8)

(ii) Briefly explain the Threads support in Solaris 2 Operating system. (8)

(a) Consider the following snapshot of a system. Execute Banker's algorithm answer

the following :

Allocation Max Available

001 001 152

100 175

135 235

063 065

001 065

(i) Is the system in a safe state? If the system is safe, show how all the process could

complete them execution successfully. Explain. (10)

(ii) If a request f rom process arrives (0, 4, 2) can the request be granted? (6)

Or

(b) Consider the following page reference string.

1, 2, 3, 4, 2, 1, 5, 6, 2, 1, 2, 3, 7, 6, 3, 2, 1, 2, 3, 6.

Calculate the number of page faults would occur f or the following page r eplacement

algorithm with frame size of 3 and 4. Initially all the frames are empty.

(i) LRU

(ii) FIFO

(iii) Optimal. (16)

(a) Assume the following workload in a system. All jobs arrive at time 0 in the order

given. Lower number is the highest priority.

Job Burst time Priority

A 10 3

B 6 1

C 7 4

D 4 2

(i) Give a Gantt chart illustrating the execution of three job using FCFS, Round Robin

(quantum = 3) and SJF. (6)

(ii) Calculate the average waiting time for each of the above scheduling algorithm.

(10)

Or

(b) (i) List five services provided by an Operating System. Explain how each provides

to the users. (8)

(ii) Explain the linked file allocation method. What are its advantages and

disadvantages? (8)

(a) (i) What is DMA transfer? Explain all the steps involved in a DMA transfer. (8)

(ii) Briefly explain the different assembly language statements. (8)

Or

(b) Briefly explain the Disk Management and Swap Space Management. (16)

(a) Discuss briefly the various issues involved in implementing Inter Process

Communication (IPC) in message passing system. (16)

Or

(b) (i) Explain the difference between External Fragmentation and Internal

Fragmentation. How to solve the fragmentation problem using Paging? (7)

(ii) Compare short term, medium term and long term scheduling. (9)

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