MCA II (Second) Semester Examination 2014-15
Course Code:MCA206 Paper ID: 0872406
Operating System
Time: 3 Hours Max. Marks: 70 Max Marks: 75
Note: Attempt six questions in all. Q. No. 1 is compulsory.
1. Answer any five of the following (limit your answer to 50 words). (4x5=20)
a) What are the functions of an operating system? Explain.
b) When do page-faults occur? Describe the actions taken by the operating system when a page-fault occurs.
c) What is Directory Structure? Discuss its relevance.
d) What is Banker’s algorithm? How is it relevant? Explain.
e) What is Page Size? What is the criterion to decide a Page Size? Explain.
f) Differentiate between Paging and Segmentation.
g) What are Semaphores? How do these help? Explain.
h) Differentiate between internal fragmentation and external fragmentation? How can you minimize the same? Explain.
2. a) What is an operating system? What are the desirable features of a good operating system? How an operating system is viewed as an extended machine? Illustrate. (5)
b) What is meant by On-line, Real-time and Multi-tasked systems? Illustrate through suitable examples. How the designing of Real-Time operating systems is viewed differently from the other operating system? (5)
3. For batch jobs A through E, arrive at a Computer System at almost the same time. They have estimated running times of 10, 6, 2, 4, and 8 minutes. Their (externally determined) priorities are 3, 5, 2, 1, and 4, respectively, with 5 being the highest priority. For each of the following scheduling algorithms, determine the mean process turnaround time. Ignore process switching overhead.
i) Round robin
ii) Priority scheduling
iii) First-come, First-served (run in order 10,6, 2, 4, 8)
iv) Shortest job first
For (i) assume that the system is multi-programmed, and to each job gets share of the CPU. For (ii) through (iv) assume that only one job at a time runs, until finishes. All jobs are completely CPU bound. (10)
4. a) What do you mean by process management? What are different process management functions of the operating system? Explain the life-cycle of a process. (5)
b) What is a process scheduler? How preemptive and non-preemptive scheduling differ from each other? State why strict non-preemptive scheduling is unlikely to be used in a Computer System. (5)
5. a) What is meant by synchronization? How the synchronization tools help in offering a correct solution for 'Readers and Writers' problem? Explain. (5)
b) What is mutual exclusion? What are the necessary and sufficient conditions for deadlock? (5)
6. a) Describe Belady’s anomaly, and provide an example that illustrates anomalous behavior of FIFO. (4)
b) What is a Swapping System? Consider a swapping system in which memory of the following hole sizes in memory order: 10K, 4K, 20K, 18K, 7K, 9K, 12K, and 15K. Which hole is taken for successive requests of: i) 12K ii) 10K iii) 9K
for First-Fit ? Repeat the same for Best-Fit, Worst-Fit, and Next-Fit. (6)
7. a) What is the cause of thrashing? How does the system detect thrashing? Once it detects thrashing, what can the system do to eliminate this problem? (5)
b) What are Page Replacement algorithms? Compare these algorithms indicating their benefits. (5)
8. What do you understand by disk scheduling? What are various disk scheduling algorithms? Compare these algorithms highlighting their suitability. (10)