NPTEL Operating System Fundamentals Week 12 Assignment Answers 2024

1. Suppose that a disk drive has 200 cylinders numbered 0 to 199. Consider a disk queue with I/O requests on the following cylinders in their arriving order: 54, 95, 73, 130, 25, 48, 110, 30, 45, 180, and 190. The disk head is assumed to be at cylinder 24. Starting from the current head position, what is the total distance (in cylinders) the disk arm moves to satisfy all the pending requests for the FCFS disk-scheduling algorithm?

(A) 580 cylinders
(B) 589 cylinders
(C) 643 cylinders
(D) 570 cylinders
(E) 585 cylinders

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2. In a demand-paging system, the paging device has an average latency of 6ms, seek time of 5ms, and transfer time of 0.1ms. The disk has a queue of waiting processes. The average waiting time is 5ms. If the memory access time is 150ns and the page fault rate is 10%. The effective memory access time is

(A) 1.61ms
(B) 1.22ms
(C) 2.712ms
(D) 1.50ms
(E) 1.45ms

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3. Suppose that a disk drive has 500 cylinders numbered 0 to 499. The drive currently serves a request at cylinder 143; the previous request was at cylinder 125. The queue of pending requests, in FIFO order, is 86, 170, 213, 474, 148, 109, 222, 450, and 330. Starting from the current head position, what is the total distance (in cylinders) the disk arm moves to satisfy all the pending requests for the SSTF disk-scheduling algorithm?

(A) 680 cylinders
(B) 580 cylinders
(C) 700 cylinders
(D) 750 cylinders
(E) 719 cylinders

Answer :-

4. Suppose that a disk drive has 140 cylinders numbered 0 to 139. Consider a disk queue with requests for I/O to blocks on cylinders 6, 10, 12, 54, 97, 73, 128, 15, 44, 110, 34, and 45 in that order. Assume that the head is moving toward decreasing the order of the cylinder numbers. Initially, the disk head is at cylinder 20. Starting from the current head position, what is the total distance (in cylinders) the disk arm moves to satisfy all the pending requests for the SCAN disk-scheduling algorithm?

(A) 150 cylinders
(B) 155 cylinders
(C) 158 cylinders
(D) 165 cylinders
(E) 170 cylinders

Answer :-

5. Suppose that a disk drive has 500 cylinders numbered 0 to 499. Consider a disk queue with requests for I/O to blocks on cylinders 10, 120, 147, 312, 180, 444, 355, 470, 290, and 170, in that order. Assume that the head is moving toward decreasing the order of the cylinder numbers. Initially, the disk head is at cylinder 100. Starting from the current head position, what is the total distance (in cylinders) the disk arm moves to satisfy all the pending requests for the C-SCAN disk-scheduling algorithm?

(A) 1328 cylinders
(B) 1220 cylinders
(C) 1350 cylinders
(D) 1380 cylinders
(E) 1280 cylinders

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6. Suppose that a disk drive has 400 cylinders numbered 0 to 399. Consider a disk queue with I/O requests on the following cylinders in their arriving order: 26, 120, 226, 354, 197, 373, 228, 315, 244, 110, 34, and 45. The read/write head is positioned at cylinder 123 and moving in the direction of decreasing cylinder number. Starting from the current head position 123, what is the total distance (in cylinders) the disk arm moves to satisfy all the pending requests for the LOOK disk-scheduling algorithm?

(A) 345 cylinders
(B) 245 cylinders
(C) 444 cylinders
(D) 440 cylinders
(E) 340 cylinders

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7. Suppose that a disk drive has 200 cylinders numbered 0 to 199. Consider a disk queue with I/O requests on the following cylinders in their arriving order: 54, 95, 73, 130, 25, 48, 110, 30, 45, 180, and 190. The read/write head is positioned at cylinder 43 and moving in the direction of decreasing cylinder number. Starting from the current head position 43, what is the total distance (in cylinders) the disk arm moves to satisfy all the pending requests for the C-LOOK disk-scheduling algorithm?

(A) 328 cylinders
(B) 324 cylinders
(C) 320 cylinders
(D) 316 cylinders
(E) 312 cylinders

Answer :-

8. Choose the disk space allocation methods that allow efficient random access to file blocks and minimise external fragmentation.

(A) Contiguous Allocation
(B) Linked Allocation
(C) Indexed Allocation
(D) File Allocation Table (FAT)
(E) Free Space Management

Answer :-

9. When the object files have been linked properly and are ready to run, they are known as

(A) archive files
(B) batch files
(C) object files
(D) executable files
(E) library files

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10. RAID structure is used to

(A) improve the performance of the data storage system
(B) improve the reliability of the data storage system
(C) make the data storage system fault-tolerant
(D) improve the data recovery
(E) All of the above