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Previous Year Exam Questions for Operating Systems - OS of 2017 - bput by Verified Writer

  • Operating Systems - OS
  • 2017
  • PYQ
  • Biju Patnaik University of Technology Rourkela Odisha - BPUT
  • Information Technology Engineering
  • B.Tech
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Registration No: Total Number of Pages: 03 B.Tech. PIT5I101 5TH Semester Regular Examination 2017-18 Operating System BRANCH: IT Time: 3 Hours Max Marks: 100 Q.CODE: B480 Answer Question No.1 and 2 which are compulsory and any four from the rest. The figures in the right hand margin indicate marks. Q1 a) b) c) d) e) f) Answer the following questions: multiple type or dash fill up type Process is a.program in High level language kept on disk b.contents of main memory c.a program in execution d.a job in secondary memory e. None of the above The strategy of allowing processes that are logically runnable to be temporarily suspended is called a. preemptive scheduling b. non preemptive scheduling c. shortest job first d. first come first served e.None of the above Interprocess communication a. is required for all processes b. is usually done via disk drives c. is never necessary, d. allows processes to synchronize activity The time required to create a new thread in an existing process is: a. greater than the time required to create a new process b. less than the time required to create a new process c. equal to the time required to create a new process d. none of the mentioned User-Friendly Systems are: a. required for object-oriented programming b. easy to develop c. common among traditional mainframe operating systems d. becoming more common e. None of the above Page stealing a.is a sign of an efficient system b.is taking page frames from other working sets c. should be the tuning goal d. is taking larger disk spaces for pages paged out e. None of the above (2 x 10)

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g) h) i) j) Q2 a) b) c) d) e) f) g) h) i) j) Q3 a) The LRU algorithm a.pages out pages that have been used recently b.pages out pages that have not been used recently c. pages out pages that have been least used recently d. pages out the first page in a given area e. None of the above Thrashing a.is a natural consequence of virtual memory systems b. can always be avoided by swapping c. always occurs on large computers d. can be caused by poor paging algorithms e. None of the above At a particular time of computation the value of a counting semaphore is 7.Then 20 P operations and 15 V operations were completed on this semaphore.The resulting value of the semaphore is : a.42 b.2 c.7 d.12 The memory allocation scheme subject to "external" fragmentation is a. segmentation b. swapping c. pure demand paging d. multiple contiguous fixed partitions e. None of the above Answer the following questions: Short answer type Explain the main purpose of an operating system? What are the advantages of multiprocessor system? What is scheduling? What criteria affects the scheduler’s performance? What is binary semaphore? What is its use? What necessary conditions can lead to a deadlock situation in a system? What are the benefits of multithreaded programming? What is demand paging? What are overlays? What is cycle stealing? What is the function of dispatcher? b) (10) Consider the following set of processes: ProcessArrival timeBurst timepriority P1 P2 P3 P4 0 1 2 3 6 4 5 8 (2 x 10) 3 1 2 4 Draw Gantt charts and find the average waiting and average turnaround time using shortest remaining time first(SRTF) and preemptive priority scheduling. If the scheduler takes 0.2 unit of cpu time in context switching, calculate the percentages of cpu time wasted in each case. Define the different states of a process with diagram. Explain the need of process suspension. (5)

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Q4 a) b) What is a directory? Define any two ways to implement the directory. What is real time operating system? What is the different between hard real time and soft real time operating system? (10) (5) Q5 a) What are deadlocks? Explain the different methods for dealing with deadlocks. Consider the following snapshot of a system: AllocationMaxAvailable R1 R2 R3 R1 R2 R3 R1 R2 R3 P1 2 2 3 3 6 8 4 3 10 P2 2 0 3 4 3 3 P3 1 2 4 3 4 4 Answer the following questions using banker’s algorithm. (a) What is the content of the matrix need? (b) Is the system in a safe state? (c) If the request from process P2 arrives for (2, 1, 0), can the request granted immediately? Differentiate between user thread and kernel thread. What is thread cancellation? (10) Suppose the moving head disc with 200 tracks is currently serving a request for track 143 and has just finished a request for track 125. If the queue of request is kept in FIFO order 86, 147, 91, 177, 94,150. What is the total head movement for the following scheduling? a. FCFS b. SSTF c. C-scan Explain the need of process synchronization. How can the inter process communication be achieved? (10) a) What do you mean by belady’s anomaly? Which algorithm suffers from belady’s anomaly? Consider the following page reference string 1, 2, 3, 4, 2, 1, 5, 6, 2, 1, 2, 1, 5, 6. How many page fault would occur for the following replacement algorithms, assuming three frames? (1) LRU page replacement (2) optimal page replacement (10) b) Explain short term, long term and medium term scheduling. Describe the differences among them. (5) a) What is bounded buffer problem? Discuss briefly with the help of producer and consumer process. Draw and explain process control block (PCB) with all its components. Also brief why context switching is an overhead in the system. (10) Discuss various file allocation strategies for disk space management. What criteria should be used in deciding which strategy is best utilize for a particular file? What are the different techniques to remove fragmentation in case of multiprogramming with fixed partitions and variable partitions? (10) b) Q6 a) b) Q7 Q8 b) Q9 a) b) (5) (5) (5) (5)

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