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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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B.E/B.Tech.DEGREE EXAMINATION,NOVEMBER/DECEMBER 2004.

Fifth Semester

Computer Science and Engineering

CS 333 – OPERATING SYSTEMS

Time: Three hours Maximum:100 marks

Answer ALL questions

PART A – (10* 2= 20 marks)

1. What is Time Sharing System?

2. What is the main advantage of the layered appr oach to system design.

3. What is job scheduler? What is CPU scheduler?

4. What are the various process states?Depict process state diagram.

5. Explain any four scheduling criteria involved in CPU scheduling.

6. Consider a logical address space of eight pages of 1024 words each, mapped

onto a physical memory of 32 Frames. How many bits are there in logical

address?

7. What is sequential address method? Mention its merits and demerits.

8. Define single level directory structure. Give one example.

9. What is a bit vector?

10. Mention any two features of linux file system.

PART B - ( 5 * 16 = 80 marks )

11. (i) Describe Working-Set model. (10)

(ii) Describe paging with illustrative example. (6)

12. (a) (i) Consider the following set of processes , with the length of the CPU

burst time given in milliseconds.

Process Burst time Priority

P1 8 3

P2 3 1

P3 4 4

P4 2 2

P5 6 5

The processes are assumed to have arrived in the order P1, P2, P3,

P4 and P5 all at time 'O'.

(1) Draw four Gantt charts illustrating the execution of these

processes using FCFS, SJF,A nonpreemptive priority (a

smaller priority number implies a higher priority) and RR

(quantum = 2) scheduling.

(2) What is the turn around time of each process f or each of the

scheduling algorithms in part (1).

(3) What is the waiting time of each process for each of the

scheduling algorithms in part (1).

(4) Which of the schedules in part (1) results in the minimal

average waiting time(over all processes) (12)

(ii) Explain the three requirements that a solution to critical-section

problem must satisfy. (4)

Or

(b) (i) Describe an algorithm which satisfies all the conditions of critical

section problem and also prove how it satisfies all the conditions.

(6)

(ii) Describe deadlock prevention methods

(1) Hold and wait

(2) Circular wait

(3) No preemption. (10)

13. (a) (i) Describe internal and external fragmentation with illustrative

examples. (8)

(ii) Describe segmentation with its hardware. (8)

Or

(b) (i) Describe multilevel paging with example. (8)

(ii) Describe hardware support of paging with TLB. (8)

14. (a) Describe place replacement algorithms

(i) FIFO algorithm

(ii) Optimal algorithm