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The Fall 2005 exam for the Operating System Concepts course (CS 471) at Old Dominion University. The exam consists of five questions covering various topics such as page replacement algorithms, virtual memory management, disk scheduling algorithms, file access matrix implementations, and security attacks. Students are required to write only in the provided spaces and use a black pen.
Typology: Exams
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USE A BLACK PEN TO ANSWER THE QUESTIONS
DO NOT WRITE HERE
(a) On a disk, space is allocated using indexed allocation. If a file F1 is allocated the following blocks (in that order), show the contents of the directory for F1 and the index block for F (located in block 200). Blocks allocated to f1: 15, 9, 210, 13, 35, 27, 96, 230 WORK AREA
(b) Answer question (a) assuming shortest-job-first scheduling with preemption.
(b) In the same system, free space on the disk is managed using link list. If the following blocks are the only blocks that are free, show how the free space will be represented. 23, 45, 78, 190, 245, 997, 1234
WORK AREA:
Question 3.
(a) Suppose that a disk drive has 8000 cylinders, numbered 0..7999. The drive is currently serving a request at cylinder 250, and the previous request was at cylinder 320. The queue of pending requests, in FIFO order, is: 500, 200, 750, 50, 4000 Starting from the current head position, what is the total distance (in cylinders) that the disk arm moves to satisfy all the pending requests for SCAN disk-scheduling algorithm WORK AREA:
(b) Answer (a) above assuming SSTF (Shortest seek time first) disk-scheduling algorithm.
WORK AREA:
Question 5.
(a) Explain how cache consistency is maintained in NFS and AFS file servers. WORK AREA:
(b) 100, 150, 200 are the timestamps of processes P1, P2, and P3, respectively. Currently, resource R1 is held by P2. Both P1 and P3 (in that order) also made requests for R1. Discuss the outcome of the requests from P1 and P3 under (i) Wait-die scheme (ii) Wound-wait scheme. WORK AREA: