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Code No: V3222/R07

III B.Tech II Semester Regular & Supplementary Examinations, April/May - 2012 OPERATING SYSTEMS

(Computer Science & Engineering) Time: 3 Hours Max Marks: 80

Answer any FIVE Questions All Questions carry equal marks

*****

1. List and explain the different CPU scheduling algorithms with example. [16]

2. a) What is multiprogramming? Explain. b) What are the responsibilities of OS in file management? c) What is critical section problem? Write a solution to the Bounded-buffer producer-consumer problem using semaphores. [4+4+8]

3. a) With suitable example, explain SSTF disk scheduling algorithm. b) Discuss the schemes for defining logical structure of a directory. [8+8]

4. a) What is a system call? Explain in brief the types of system calls provided by OS. b) Give Banker's algorithm and explain with suitable example. [8+8]

5. a) List and explain the techniques for structuring the page table. b) Explain the following program threats. i) Trojan horse ii) Stack and Buffer overflow [8+8]

6. a) What is serializability? Explain about locking protocol b) Explain the computer-security classifications. [8+8]

7. a) Discuss the performance issues of tertiary-storage. b) Explain the following techniques for structuring the page table in detail.

i) Hierarchical paging ii) Inverted page table [8+8]

8. a) Explain the different options for breaking a deadlock. b) How do caches help improve performance? Why do system not use more or larger caches if they are so useful? [8+8]

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Set No: 1

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Code No: V3222/R07

III B.Tech II Semester Regular & Supplementary Examinations, April/May - 2012 OPERATING SYSTEMS

(Computer Science & Engineering) Time: 3 Hours Max Marks: 80

Answer any FIVE Questions All Questions carry equal marks

*****

1. a) Discuss about the operating system components. b) What is semaphore? What is meant by counting semaphore and binary semaphore? Discuss mutual exclusion implementation using semaphore. [8+8]

2. a) Explain the multithreaded models for user and kernel threads. b) Explain the Readers-Writers problem and give the solution for synchronization using semaphores. [8+8]

3. a) What is a stable storage? How to implement such storage? b) Explain in detail the Bankers algorithm with suitable example. [8+8]

4. a) Given memory partitions of 100 KB, 500 KB, 200 KB, 300 KB, and 600KB (in order), how would each of the first-fit, best-fit, and worst-fit algorithms place processes of 236 KB, 543 KB, 92 KB and 350 KB (in order)? Which algorithm makes the most efficient use of memory? b) What is RAID? Explain the concept of improvement of reliability via redundancy and improvement in performance via parallelism. [8+8]

5. a) Consider the following set of processes, with the length of the CPU-burst time given in milliseconds:

Process Burst Time P1 3 P2 1 P3 5 P4 2 P5 7

The processes are assumed to have arrived in the order P1, P2, P3, P4, P5 all at time 0. i) Draw four Gnatt charts illustrating the execution of these processes using SJF, and

RR (quantum = 1) scheduling. ii) What is the waiting time of each process for each of the scheduling algorithms in part (i)? b) What is segmentation? Explain [8+8]

6. a) Explain about the interprocess communication. b) Explain the following system threats i) Viruses ii) Denial of service [8+8]

7. a) Discuss about the deadlock prevention approach. b) Explain the following methods of allocating disk space

i) Linked allocation ii) Indexed allocation [8+8]

8. a) Discuss about the language-based protection. b) Explain the different methods of maintaining free space list. [8+8]

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Set No: 2

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Code No: V3222/R07

III B.Tech II Semester Regular & Supplementary Examinations, April/May - 2012 OPERATING SYSTEMS

(Computer Science & Engineering) Time: 3 Hours Max Marks: 80

Answer any FIVE Questions All Questions carry equal marks

*****

1. a) Explain the terms multiprogramming and multitasking. b) Explain the different file access control methods. [8+8]

2. a) What is meant by CPU scheduling? Explain the criteria for comparing CPU scheduling algorithms. b) Explain the common approaches for authenticating a user identity. [8+8]

3. a) Explain the fork( ) and exec( ) system calls. b) What is meant by atomic transactions? Explain log-based recovery algorithm to ensure atomicity. [8+8]

4. What are the different types of disk scheduling? Explain each with example. [16]

5. a) List and explain the different operating system services b) Explain the computer-security classifications. [8+8]

6. a) Explain the concept of file mounting. b) What is a serial schedule? Explain a locking protocol to ensure serializability. [8+8]

7. a) What is deadlock avoidance approach? Explain safe state and unsafe state with example. b) Explain the difference between external fragmentation and internal fragmentation.

c) Consider a logical-address space of eight pages of 2048 words each, mapped onto a physical memory of 16 frames. i) How many bits are in the logical address?

ii) How many bits are in the physical address? [8+4+4]

8. a) Explain the services provided by kernel I/O subsystem. b) Given memory partitions of 500 KB, 100 KB, 200 KB, 300 KB, and 600KB (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+8]

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Set No: 3

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Code No: V3222/R07

III B.Tech II Semester Regular & Supplementary Examinations, April/May - 2012 OPERATING SYSTEMS

(Computer Science & Engineering) Time: 3 Hours Max Marks: 80

Answer any FIVE Questions All Questions carry equal marks

*****

1. a) Explain the layered approach and microkernel approach to system design. b) Explain the linked method of allocating disk space with its advantages and disadvantages. [8+8]

2. a) Discuss about revocation of access rights in detail. b) Describe the differences among short-term, medium-term, and long-term scheduling. [8+8]

3. a) What is thread? What are the benefits of multithreaded programming? b) What is file system mounting? How it is done? c) Explain the process of booting the system. [8+4+4]

4. a) What is real time operating system? b) Discuss about the tree-structured directory structure. c) Explain the following capability-based systems

i) Hydra ii) Cambridge CAP System [4+4+8]

5. a) What is the need of monitor? How a monitor is implemented using semaphore? b) Discuss about RAID structure. [8+8]

6. a) Discuss about the paging hardware with TLB. b) What is safe state and unsafe state? Discuss about the deadlock avoidance. [8+8]

7. a) Discuss about swap-space management. b) What is the dining-philosopher's problem? Give its solution. [8+8]

8. a) What is page fault? Discuss the following page replacement algorithms. i) LRU replacement ii) FIFO replacement b) What is STREAMS? Explain. [8+8]

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Set No: 4