A directory of Objective Type Questions covering all the Computer Science subjects. Here you can access and discuss Multiple choice questions and answers for various compitative exams and interviews.

71. Consider a disk pack with 16 surfaces, 128 tracks per surface and 256 sectors per track. 512 bytes of data are stored in a bit serial manner in a sector. The capacity of the disk pack and the number of bits required to specify a particular sector in the disk are respectively:
a. 256 Mbyte, 19 bits
b. 256 Mbyte, 28 bits
c. 512 Mbyte, 20 bits
d. 64 Gbyte, 28 bit
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Answer: (a).256 Mbyte, 19 bits

72. Suppose a disk has 201 cylinders, numbered from 0 to 200. At some time the disk arm is at cylinder 100, and there is a queue of disk access requests for cylinders 30, 85, 90, 100, 105, 110, 135 and 145. If Shortest-Seek Time First (SSTF) is being used for scheduling the disk access, the request for cylinder 90 is serviced after servicing ____________ number of requests.
a. 1
b. 2
c. 3
d. 4
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Answer: (c).3

73. A device with data transfer rate 10 KB/sec is connected to a CPU. Data is transferred byte-wise. Let the interrupt overhead be 4 msec. The byte transfer time between the device interface register and CPU or memory is negligible. What is the minimum performance gain of operating the device under interrupt mode over operating it under program controlled mode?
a. 15
b. 25
c. 35
d. 45
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Answer: (b).25

74. Consider a disk drive with the following specifications: 16 surfaces, 512 tracks/surface, 512 sectors/track, 1 KB/sector, rotation speed 3000 rpm. The disk is operated in cycle stealing mode whereby whenever one byte word is ready it is sent to memory; similarly, for writing, the disk interface reads a 4 byte word from the memory in each DMA cycle. Memory cycle time is 40 nsec. The maximum percentage of time that the CPU gets blocked during DMA operation is:
a. 10
b. 25
c. 40
d. 50
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Answer: (b).25

75. Consider an operating system capable of loading and executing a single sequential user process at a time. The disk head scheduling algorithm used is First Come First Served (FCFS). If FCFS is replaced by Shortest Seek Time First (SSTF), claimed by the vendor to give 50% better benchmark results, what is the expected improvement in the I/O performance of user programs?
a. 50%
b. 40%
c. 25%
d. 0%
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Answer: (d).0%

76. 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 ?
a. 2^24 bytes
b. 2^32 bytes
c. 2^34 bytes
d. 2^48 bytes
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Answer: (c).2^34 bytes

77. 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 ?
a. 5.0%
b. 1.0%
c. 0.5%
d. 0.1%
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Answer: (d).0.1%

78. Using a larger block size in a fixed block size file system leads to :
a. better disk throughput but poorer disk space utilization
b. better disk throughput and better disk space utilization
c. poorer disk throughput but better disk space utilization
d. poorer disk throughput and poorer disk space utilization
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Answer: (a).better disk throughput but poorer disk space utilization

79. Which of the following requires a device driver?
a. Register
b. Cache
c. Main memory
d. Disk
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Answer: (d).Disk

80. A graphics card has on board memory of 1 MB. Which of the following modes can the card not support?
a. 1600 x 400 resolution with 256 colours on a 17-inch monitor
b. 1600 x 400 resolution with 16 million colours on a 14-inch monitor
c. 800 x 400 resolution with 16 million colours on a 17-inch monitor
d. 800 x 800 resolution with 256 colours on a 14-inch monitor
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Answer: (b).1600 x 400 resolution with 16 million colours on a 14-inch monitor

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