OS Input Output Systems

Question 21

A Unix-style i-node has 10 direct pointers and one single, one double and one triple indirect pointers. Disk block size is 1 Kbyte, disk block address is 32 bits, and 48-bit integers are used. What is the maximum possible file size ?

• 2²⁴ bytes
• 2³² bytes
• 2³⁴ bytes
• 2⁴⁸ bytes

Question 22

A hard disk with a transfer rate of 10 Mbytes/ second is constantly transferring data to memory using DMA. The processor runs at 600 MHz, and takes 300 and 900 clock cycles to initiate and complete DMA transfer respectively. If the size of the transfer is 20 Kbytes, what is the percentage of processor time consumed for the transfer operation ?

• 5.0%
• 1.0%
• 0.5%
• 0.1%

Question 23

Using a larger block size in a fixed block size file system leads to :

• better disk throughput but poorer disk space utilization
• better disk throughput and better disk space utilization
• poorer disk throughput but better disk space utilization
• poorer disk throughput and poorer disk space utilization

Question 24

Which of the following requires a device driver?

• Register
• Cache
• Main memory
• Disk

Question 25

A graphics card has on board memory of 1 MB. Which of the following modes can the card not support?

• 1600 x 400 resolution with 256 colours on a 17-inch monitor
• 1600 x 400 resolution with 16 million colours on a 14-inch monitor
• 800 x 400 resolution with 16 million colours on a 17-inch monitor
• 800 x 800 resolution with 256 colours on a 14-inch monitor

Question 26

Consider the situation in which the disk read/write head is currently located at track 45 (of tracks 0-255) and moving in the positive direction. Assume that the following track requests have been made in this order: 40, 67, 11, 240, 87. What is the order in which optimised C-SCAN would service these requests and what is the total seek distance?

• 600
• 810
• 505
• 550

Question 27

Suppose the following disk request sequence (track numbers) for a disk with 100 tracks is given: 45, 20, 90, 10, 50, 60, 80, 25, 70. Assume that the initial position of the R/W head is on track 50. The additional distance that will be traversed by the R/W head when the Shortest Seek Time First (SSTF) algorithm is used compared to the SCAN (Elevator) algorithm (assuming that SCAN algorithm moves towards 100 when it starts execution) is _________ tracks

• 8
• 9
• 10
• 11

Question 28

Consider a disk pack with a seek time of 4 milliseconds and rotational speed of 10000 rotations per minute (RPM). It has 600 sectors per track and each sector can store 512 bytes of data. Consider a file stored in the disk. The file contains 2000 sectors. Assume that every sector access necessitates a seek, and the average rotational latency for accessing each sector is half of the time for one complete rotation. The total time (in milliseconds) needed to read the entire file is _________.

• 14020
• 14000
• 25030
• 15000

Question 29

Consider a typical disk that rotates at 15000 rotations per minute (RPM) and has a transfer rate of 50 × 10⁶ bytes/sec. If the average seek time of the disk is twice the average rotational delay and the controller’s transfer time is 10 times the disk transfer time, the average time (in milliseconds) to read or write a 512 byte sector of the disk is _____________

• 6.1

Question 30

Consider a disk queue with requests for I/O to blocks on cylinders 47, 38, 121, 191, 87, 11, 92, 10. The C-LOOK scheduling algorithm is used. The head is initially at cylinder number 63, moving towards larger cylinder numbers on its servicing pass. The cylinders are numbered from 0 to 199. The total head movement (in number of cylinders) incurred while servicing these requests is:   Note : This question was asked as Numerical Answer Type.

• 346
• 165
• 154
• 173