OS QUESTIONS

1. Aging is

Ans. increasing the priority of jobs to ensure termination

in a finite time

2. In a paged segmented scheme of memory management ,the segment table itself must have a

page table because 

Ans. each segment is spread over a number of pages

3. Virtual memory is 

Ans. an illusion of an extremely large memory

4. A memory page containing a heavily used variable that was initialized very early and is in constant use is removed when the page replacement algorithm used is

Ans. FIFO

5. An address generated by memory unit is _ _ _ _ _ _ _

_ _ _ _ _ _ address

Ans. zero

6. The first fit ,best fit and the worst fit algorithm can be

used for 

Ans. contiguous allocation of memory

7. Which of the following page replacement algorithm

suffers form belady's anomaly? 

Ans. FIFO  

8. Memory management unit is _ _ _ _ _ _ _ _ _ _ _ _ _

_ _ _ _  

Ans. hardware

9. The run time mapping from virtual to physical address

is done by _ _ _

Ans. memory management unit

10. An address generated by CPU is known as _ _ _ _ _ _

_ _ _ _ _ address

Ans. Logical

11. Overlay is  

Ans. a single contiguous memory that is used in olden days

for running large programs by

swapping

12. Some computer systems support dual mode

operation - the user mode and the super visor mode.

These refers to the modes  

Ans. in which the processor and the associated hardware

operate

13. Spatial locality refers to the problem that once a

location referenced

Ans. a near by location will be referenced soon

14. Let physical address =14346 base = 4000 then

logical address is _ _ _ _ _ _ _ _

Ans. 346

15. The maximum value for logical address=y base

register value=x What is the maximumvalue for

physical address?

Ans. x+y

16. Page fault occurs when  

 Ans. The page is not in main memory

17. The size of virtual memory depends on

Ans. the size of the address bus  

18. _ _ _ _ _ _ _ _ _ _ _ algorithm searches the list of

holes and allocate the first memory area that is

large enough  

Ans. first fit

19. _ _ _ _ algorithm fits process into the hole that is

large enough to hold the process and closest in

size to the requirements of that process  

Ans. best fit

20. _ _ _ _ _ _ _ _ _ _ _ algorithm fits the process into

the largest available hole  

Ans. worst fit

21. Which of the following is an example of a SPOOLED device 

Ans. A line printer used to print the output of a number of jobs

22. _ _ _ _ _ _ _ page replacement algorithm is based on the argument that the page with the smallest count was probably just brought in and has yet

to be used.

Ans. MFU

23. In partitioned memory allocation scheme

Ans. The superiority of the first fit and best fit algorithms

depend on the sequence of memory

requests

24. To implement LRU _ _ _ _ _ _ _ _ _ data structure is used.

Ans. stack

25. Virtual memory is commonly implemented by _ _ _ 

_ _ _ _ _ _

Ans. demand paging

26. A process refers to 5 pages A,B,C,D,E in the following order A,B,C,D,A,B,E,A,B,C,D,E. if the page replacement algorithm is FIFO, the number of Page transfer with an empty internal store of 3 frames is _ _ _ _ _ _

Ans. 9

27. _ _ _ _ _ _ _ _ _ _ _ is a technique to solve the problems of internal fragmentation 

Ans. segmentation

28. A process is _ _ _ _ _ _ _ _ _ if it is spending more time paging than executing.  

Ans. thrashing

29. Replace the page that has not been used for the longest period of time.This is _ _ _ _ _ _ _ _

Ans. LRU

30. _ _ _ _ _ _ _ page replacement algorithm requires that the page with the smallest count be replaced.

Ans. LFU

31. Which of the following is true.

ans. The linkage editor links object modules and resolves

external references between them before

loading

32. Determine the number of page faults when references to pages occur in the following order 1,2,4,5,2,1,2,4. Assume that the main memory can accommodate 3 pages and the main memory already has the pages 1 and 2 with page 1 having been brought earlier than page 2(LRU algorithm is used.)  

ans. 4

33. Dirty bit is used to show the

Ans. page that is modified after being loaded into cache

Memory

34. To obtain better memory utilization ,dynamic loading is used. With dynamic loading a routine is not loaded until it is called for. For implementing

dynamic loading  

Ans. user programs can implement dynamic loading

without any special support form hardware

and OS

35. The page replacement policy that sometimes leads to more page faults when the size of the memory is increased is  

Ans. FIFO

36. In paged memory system if the page is increased then the internal fragmentation generally

Ans. becomes more

37. When total memory space is available to satisfy the requirement of the process is not contiguous

it is called _ _ _ _ _ _ _ _ _ fragmentation  

Ans. external

38. When the space with in the block is unused by the process residing in that block it is called _ _ _ _ _ _ _ _ _ fragmentation

Ans. Internal

39. _ _ _ _ _ _ _ _ _ _ _ is a technique to solve the problems of external fragmentation

Ans. paging

40. In the CPU scheduling policy is SJF the average waiting time will be _ _ _ _ _ _ (with pre emption)

Ans. 5.6ms

41.In the CPU scheduling policy is priority scheduling the average waiting time will be _ _ _ _ _ _ (with out pre emption)

Ans .10.8ms

42.In the CPU scheduling policy is FCFS the average waiting time will be _ _ _ _ _ _ _ _

Ans. 12.8 ms

43. In the CPU scheduling policy is SJF the average waiting time will be _ _ _ _ _ _ (with out preemption)

Ans. 6.8 ms

44. In the CPU scheduling policy is priority scheduling the average waiting time will be _ _ _ _ _ _

(with pre emption)

Ans .7. 6 ms

45. Pre emptive scheduling is the strategy of temporarily suspending a running process

Ans. before the cpu time slice expires

46. Which of the following scheduling algorithms gives minimum average waiting time

Ans. SJF

47. Which of the following is well suited for a time

shared OS?

Ans .round robin

48. CPU utilization may range from _ _ _ to _ _ _ _ _ percent

Ans. 0,100

49. The number of processes that are completed per unit

time is called as _ _ _ _ _ _ _

Ans. throughput

50. _ _ _ _ _ _ _ _ _ scheduler is also called as CPUscheduler

Ans .short term

51. _ _ _ _ _ _ _ _ _ scheduler is also called as JOB scheduler

Ans. long term

52. In round robin CPU scheduling as the time quantum is increased the average turn around time

Ans. varies irregularly

53. In which of the following scheduling policies does context switching never take place

Ans. FCFS

54. The amount of time processor takes to start responding is _ _ _ _ _ _ _

Ans. response time

55. The interval from the time of submission of a process to the time of completion is the _ _ _ _ _ _

Ans. turnaround time

56. The amount of time that a process spends waiting in

the ready queue is the _ _ _ _ _ _

Ans. waiting time

57. _ _ _ _ _ _ _ scheduler allocates CPU to a process

Ans. short term

58. _ _ _ _ _ _ _ _ _ _ _ _ scheduler performs swapping process

Ans. medium term

59. _ _ _ _ _ _ _ _ _ scheduler determines which jobs

are brought into memory for processing.

Ans. long term

60. Which of the following has third priority

Ans. RST6.5

61. Which of the following has fourth priority

Ans. RST5.5

62. Which of the following has second priority

Ans. RST 7.5

63. The data transfer mode of terminal is _ _ _ _ _ _ _ _ _ _

Ans .character

64. The access method of modem is _ _ _ _ _ _ _ _ _ _ _

Ans. sequential

65. Which of the following is not maskable 

Ans.TRAP

66. Which of the following has highest priority

Ans. TRAP

67. Which of the following has least priority

Ans. INTR

68. The data transfer mode of disk is _ _ _ _ _ _ _ _ _ _ 

Ans. block

69. The access method of CD-ROM is _ _ _ _ _ _ _ _ _ _ _  

Ans. random

70. Which of the following is write only

Ans. graphics controller

71. Which of the following is read & write

Ans. disk

72. CD-ROM is _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Ans. read only

73. graphics controller is _ _ _ _ _ _ _ _ _ _ _

Ans.. write only

74. Which of the following is read only 

Ans. CD-ROM

75. The transfer schedule of tape is _ _ _ _ _ _ _ _ _ _ _

Ans. synchronous

76. The transfer schedule of keyboard is _ _ _ _ _ _ _ _ 

Ans. asynchronous

77. A tape is _ _ _ _ _ _ _ _ _ _ _ _

Ans. dedicated

78. A keyboard is _ _ _ _ _ _ _ _ _ _

Ans. sharable always

79. disk is _ _ _ _ _ _ _ _ _ _

Ans. read & write

80. In a paged memory system the page hit ratio is 0.35.

The time required to access a page in

secondary memory is equal to 100ns. The time required

to access a page in primary memory is

10ns.The average time required to access a page is

Ans. 68.5ns

81. A spool is a _ _ _ _ _ _ _ _ _ that holds output for a

device such as printer, that can not accept internal data streams

Ans. Buffer

82. In a multiprogramming environment

Ans. more than one process is resident in memory

83. The hardware mechanism that enables a device to

notify the CPU is called _ _ _ _ _

Ans. Interrupt

84. _ _ _ _ _ _ _ _ _ _ is a memory area that stores data

while the calls are transferred between two

devices or between a device and an application

Ans. Buffer

85. _ _ _ _ _ _ _ _ _ is an example for storage device

Ans. tape

86. _ _ _ _ _ _ _ _ _ is an example for transmission device.

Ans. Modem

87. Which of the following is not an example for human interface device

Ans. network card

88. Pick the odd man out

Ans. modem

89. Which of the following is fastest

Ans. cache

90. A certain moving arm disk storage with one head

has following specification number of tracks /recording surface =200 disk rotation speed

=2400 rpm track storage capacity = 62500

bits The average latency time is _ _ _ _ _ _ _ _ _ _ _ _

Ans. 2.5 s

91. A certain moving arm disk storage with one head

has following specification

number of tracks /recording surface =200

disk rotation speed =2400 rpm

track storage capacity = 62500 bits

The transfer rate will be _ _ _ _ _ _ _ _ _ _ _ _

Ans. 2.5 m bits/s

92. A stream is a _ _ _ _ _ _ _ _ _ connection between a

device driver and a user level process.

Ans. full duplex

93. Pick the odd man out

Ans. device driver

94. The kernel module that controls a device is a _ _ _ __ _ _ _ _

Ans. device driver

95. Sector interleaving in disks is done by

 Ans. the OS

96. Access time is the highest in the case of

Ans. magnetic disks

97. A system call is a function called by an application to

invoke a _ _ _ _ _ _ _ service.

Ans. Kernel

98. Which of the following is not related to the basic

hardware elements involved in I/O

Ans. Kernel

99. Which of the following is not related to the kernels

I/O subsystem service

Ans.Interpretation

100. A disk queue with requests for I/O to blocks on

cylinders. 98, 183, 37, 122, 14, 124, 65, 67 in

that order. If the disk is initially at cylinder 53.The total

head movement is _ _ _ _ _

cylinders( SSTF)

Ans. 236