Computer Science - Operation System – Multiple Choice Question

Question 1 of 94

1. Question

Virtual memory is

an extremely large main memory
an extremely large secondary memory
an illusion of an extremely large memory
a type of memory used in super computers

Question 2 of 94

2. Question

Spatial locality refers to the problem that once a location is referenced

it will not be referenced agian
it will be referenced agian
a nearby location will be referenced soon
none of the above

Question 3 of 94

3. Question

Which of the following is an example of a SPOOLED device?

The terminal used to enter the input data for a program being executed.
The secondary memory device in a virtual memory system.
A line printer used to print the output of a number of jobs
None of the above

Question 4 of 94

4. Question

Page fault occurs when

the page is corrupted by application software
the page is in main memory
the page is not in main memory
one tries to divide a number by 0

Question 5 of 94

5. Question

Overlay is

a part of an operating system
a specific memory location
a single contiguous memory that was used in the olden days for running large programs by swapping.
overloading the system with many user files

Question 6 of 94

6. Question

Determine the number of page faults when references to pages occur in the 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. (Assume LRU algorithm is used)

3
5
4
none of the above

Question 7 of 94

7. Question

Concurrent processes are processes that

do not overlap in time
overlap in time
are executed by a processor at the same time
none of the above

Question 8 of 94

8. Question

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

FIFO
LRU
no such policy exists
none of the above

Question 9 of 94

9. Question

The only state transition that is initialed by the user process itself is

block
dispatch
wakeup
none of the above

Question 10 of 94

10. Question

Working set (t,k) at an instant of time, t, is the set of

k future references that the operating system will make
future references that the operating system will make in the next 'k' time units
k references with high frequency
pages that have been referenced in the last k time units

Question 11 of 94

11. Question

Fragmentation is

dividing the secondary memory into equal sized fragments
dividing the main memory into equal-sized fragments
fragments of memory words used in a page
fragments of memory words unused in a page

Question 12 of 94

12. Question

Which of the following are real-time systems?

An on-line railway reservation system
A process control system
Aircraft control system
Payroll processing system

Question 13 of 94

13. Question

Dijkstra’s banking algorithm in an operating system solves the problem of

deadlock avoidance
deadlock recovery
mutual exclusion
context switching

Question 14 of 94

14. Question

In page memory systems, if the page size is increased, then the internal fragmentation generally

becomes less
becomes more
remains constant
none of the above

Question 15 of 94

15. Question

An operating system contains 3 user processes each requiring 2 units of resource R. The minimum number of units of R such that no dead lock will ever occur is

3
4
5
1

Question 16 of 94

16. Question

Critical region is

a part of the operating system which is not allowed to be accessed by any process
a set of instructions that access common shared resource which exclude one another in time
the portion of the main memory which can be accessed only by one process at a time
none of the above

Question 17 of 94

17. Question

Kernel is

considered as the critical part of the operating system
the software which monitors the operating system
the set of primitive functions upon which the rest of operating system functions are built up
none of the above

Question 18 of 94

18. Question

With a single resource, deadlock occurs

if there are more than two processes competing for that resource
if there are only two processes competing for that resource
if there is single processes competing for that resource
none of the above

Question 19 of 94

19. Question

Necessary conditions for deadlock are

non-preemption and circular wait
Mutual exclusion and partial allocation
both (a) and (b)
none of the above

Question 20 of 94

20. Question

In a time-sharing operating system, when the time slot given to a process is completed, the process goes from the RUNNING state to the

BLOCKED state
READY state
SUSPENDED state
TERMINATED state

Question 21 of 94

21. Question

At a particular time, the value of a counting semaphore is 10. It will become 7 after

3 V operations
3 P operations
5 V operations and 2 P operations
13 P operations and 10 V operations

Question 22 of 94

22. Question

Supervisor call

is a call made by the supervisor of the system
is a call with control functions
are privileged calls that are used to perform resource management functions, which are controlled by the operating system.
is a call made by the someone is working in root directory

Question 23 of 94

23. Question

Semaphores are used to solve the problem of

race condition
process synchronization
mutual exclusion
none of the above

Question 24 of 94

24. Question

If the property of locality of reference is well pronounced in a program

the number of the page faults will be more
the number of the page faults will be less
the number of the page faults will remain the same
execution will be faster

Question 25 of 94

25. Question

At a particular time of computation, the value of a counting semaphore is 7.Then 20 p operations and ‘x’ V operations were completed on this semaphore. If the final value of the semaphore is 5, x will be

15
22
18
13

Question 26 of 94

26. Question

Pre-emptive scheduling, is the strategy of temporarily suspending a running process

before the CPU time slice expires
to allow starving processes to run
when it requests I/O
none of the above

Question 27 of 94

27. Question

Mutual exclusion problem occurs

between two disjoint processes that do not interact
among processes that share resources
among processes that do not use the same resource
none of the above

Question 28 of 94

28. Question

Sector interleaving in disks is done by

the disk manufacturer
the disk controller cord
the operating system
none of the above

Question 29 of 94

29. Question

Memory protection is of no use in a

single user system
non-multiprogramming system
non-multitasking system
none of the above

Question 30 of 94

30. Question

Some computer systems support dual mode operation the user mode and the supervisor or monitor mode. These refer to the modes

by which user programs handle their data
by which the operating system executes user programs
in which the processor and the associated hardware operate.
of memory access

Question 31 of 94

31. Question

Disk scheduling involves deciding

which disk should be accessed next
the order in which disk access requests must be serviced
the physical location where files should be accessed in the disk
none of the above

Question 32 of 94

32. Question

A computer system has 6 tape drives, with ‘n’ processes competing for them, Each process may need 3 tape drives. The maximum value of ‘n’ for which the system is guaranteed to be deadlock free is

2
3
4
1

Question 33 of 94

33. Question

Dirty bit is used to show the

page with corrupted data
wrong page in the memory
page that is modified after being loaded into cache memory
page that is less frequently accessed

Question 34 of 94

34. Question

Fence register is used for

CPU protection
memory protection
file protection
all of the above

Question 35 of 94

35. Question

Which of the following is a service not supported y the operation system?

protection
Accounting
Compilation
I/O operation

Question 36 of 94

36. Question

The first-fit, best-fit and the worst-fit algorithm can be used for

contiguous allocation of memory
linked allocation of memory
indexed allocation of memory
all of the above

Question 37 of 94

37. Question

Which of the following are single-user operating systems?

MS-DOS
UNIX
XENIX
OS/2

Question 38 of 94

38. Question

In Round Robin CPU scheduling, as the time quantum is increased, the average turn around time

increases
decreases
remains constant
varies irregularly

Question 39 of 94

39. Question

In a multiprogramming environment

the processor executes more than one process at a time
the programs are developed by more than one person
more than one process resides in the memory
a single user can execute many programs at the same time.

Question 40 of 94

40. Question

Which of the following are true?

A re-entrant procedure can be called any number of times
A re-entrant procedure can be called even before the procedure has not returned from its previous call.
Re-entrant procedure cannot be called recursively.
Re-entrant procedure can be called recursively.

Question 41 of 94

41. Question

In a paged memory, the page hit ratio is 0.35. The time required to access a page in secondary memory is equal to 100 ns. The time required to access a page in primary memory is 10 ns. The average time required to access a page is

3.0 ns
68.0 ns
68.5 ns
78.5 ns

Question 42 of 94

42. Question

A state is safe if the system can allocate resources to each process (up to its maximum) in some order and still avoid deadlock.

Which of the following are true?

Deadlocked state is unsfe
Unsafe state may lead to a deadlock situation.
Unsafe state must lead to a deadlock situation
Deadlocked state is a subset of unsafe state

Question 43 of 94

43. Question

The size of the virtual memory depends on the size of the

data bus
main memory
address bus
none of the above

Question 44 of 94

44. Question

In a multi-user operating system.20 requests are made to use a particular resource per hour, on an average. The probability that no requests are made in 45 minutes is

e^-15
e^-5
1 - e^-5
1 - e^-10

Question 45 of 94

45. Question

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

Round-robin
Shortest job first
Pre-emptive
First-cum-first-served

Question 46 of 94

46. Question

Suppose that a process is in ‘BLOCKED’ state waiting for some I/O service. When the service is completed, it goes to the

RUNNING state
READY state
SUSPENDED state
TERMINATED state

Question 47 of 94

47. Question

In which of the following directory systems, is it possible to have multiple complete paths for a file starting from the root directory?

Single level directory
Two level directory
Tree structured directory
Acyclic graph directory

Question 48 of 94

48. Question

In a system that does not support swapping

the compiler normally binds symbolic addresses (variables) to relocatable addresses.
the compiler normally binds symbolic addresses to physical addresses.
the loader binds relocatable addresses to physical addresses.
binding of symbolic addresses to physical addresses normally takes place during execution.

Question 49 of 94

49. Question

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,

special support from hardware is essential
special support from operating system is essential
special support from both hardware and operating system are essantial
user programs can implement dynamic loading without any special support from the operating system or the hardware

Question 50 of 94

50. Question

Which of the following is true?

The linkage editor is used to edit programs which have to be later lined together.
The linkage editor links object modules during compiling or assembling.
The linkage editor links object modules and resolves external references between them before loading.
The linkage editor resolves external references between the objects modules during execution time.

Question 51 of 94

51. Question

Which of the following is true?

Overlays are used to increase the size of physical memory.
Overlays are used to increase the logical address space.
When overlays are used, the size of a process is not limited to the size of physical memory.
overlays are used whenever the physical address space is smaller than the logical address space.

Question 52 of 94

52. Question

If the CPU scheduling policy is FCFS, the average waiting time will be

12.8 ms
8 ms
16 ms
none of the above

Question 53 of 94

53. Question

If the CPU scheduling policy is SJF, the average waiting time (without pre-emption) will be

12.8 ms
6.8 ms
17 ms
none of the aboe

Question 54 of 94

54. Question

If the CPU scheduling policy SJF with pre-emption, the average waiting time will be

8 ms
14 ms
5.6 ms
none of the above

Question 55 of 94

55. Question

If the CPU scheduling policy is priority scheduling without pre-emption, the average waiting time will be

12.8 ms
11.8 ms
10.8 ms
none of the above

Question 56 of 94

56. Question

If the CPU scheduling policy is priority scheduling with pre-emption,k the average waiting time will be

19 ms
7.6 ms
8 ms
none of the above

Question 57 of 94

57. Question

In partitioned memory allocation scheme, the

best fit algorithm is always better than the first fit algorithm.
first fit algorithm is always better than the best fit algorithm.
superiority of the first fit and best-fit algorithms depend on the sequence of memory requests.
none of the above

Question 58 of 94

58. Question

Cascading termination refers to termination of all child processes before the parent terminates

normally
abnormally
normally or abnormally
none of the above

Question 59 of 94

59. Question

For implementing a multiprogramming operating system

special support from processor is essential
special support from processor is not essential
cache memory must be available
more than one processor must be available

Question 60 of 94

60. Question

Consider a system having ‘m’ resources of the same type. These resources are shared by 3 processes A, B, C, which have peak time demands of 3, 4, 6 respectively. The minimum value of ‘m’ that ensures that dead lock will never occur is

11
12
13
14

Question 61 of 94

61. Question

A system has 3 processes sharing 4 resources. If each process needs a maximum of 2 units then, deadlock

can never occur
may occur
has to occur
none of the above

Question 62 of 94

62. Question

‘m’ processes share ‘n’ resources of the same type. The maximum need of each process doesn’t exceed ‘n’ and the sum all their maximum needs is always less than m+n. In this set up deadlock.

can never occur
may occur
has to occur
none of the above

Question 63 of 94

63. Question

A process refers to 5 pages, A, B, C, D and E in the order – A; B; C; D; A; B; which transfer with an empty internal store of 3 frames is

8
10
9
7

Question 64 of 94

64. Question

Distrubuted systems should

meet prescribed time constraints
aim better resource sharing
aim better system utilization
aim low system overhead

Question 65 of 94

65. Question

The main function of shared memory is to

use primary memory efficiently
do intra process communication
do inter process communication
none of the above

Question 66 of 94

66. Question

Which of the following is the most suitable scheduling scheme in a real-time operating system?

round-robin
first-come-first-served
pre-emptive scheduling
random scheduling

Question 67 of 94

67. Question

In Question number 63, if the number of available page frames is increased to 4 then the number of page transfers

decreases
increases
remains the same
none of the above

Question 68 of 94

68. Question

‘Aging’ is

Keeping track of cache contents
Keeping track of what pages are currently residing in the memory.
Keeping track of how many times a given page is referenced.
increasing the priority of jobs to ensure termination in finite time.

Question 69 of 94

69. Question

If there are 32 segments, each of size 1 k bytes, then the logical address should hav

13 bits
14 bits
15 bits
16 bits

Question 70 of 94

70. Question

Disk requests come to a disk driver for cylinders in the order 10, 22, 20, 2, 40, 6 and 38 at a time when the disk drive is reading from cylinder 20. the seed time is 6 ms per cylinder. The total seek timer, if the disk arm scheduling algorithm is first-ome-first-served is

360 ms
850 ms
900 ms
none of the above

Question 71 of 94

71. Question

In question 70, if the scheduling algorithm is the closest cylinder next, then the total seek time will be

360 ms
876 ms
850 ms
900 ms

Question 72 of 94

72. Question

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 (assume that the head can move from one track to another only by traversing the entire track) is

2.5 s
2.9 s
3.1 s
3.6 s

Question 73 of 94

73. Question

Memory protection is normally done by the

processor and the associated hardware
operating system
compiler
user program

Question 74 of 94

74. Question

Which of the following scheduling algorithms gives minimum average waiting time?

FCFS
SJF
Round-robin
Priority

Question 75 of 94

75. Question

In question number 72, the transfer rate will be

2.5 Mbits/s
4.25 Mbits/s
1.5 Mbits/s
3.75 Mbits/s

Question 76 of 94

76. Question

In a paged segmented scheme of memory management, the segment table itself must have a page table because

the segment table is often too large to fit in one page
each segment is spread over a number of pages
segment tables point to page tables and not to the physical location of the segment
the processor's description base register points to a page table

Question 77 of 94

77. Question

Which of the following page replacement algorithms suffers from Belady’s anomaly?

Optimal replacement
LRU
FIFO
Both optimal replacement and FIFO

Question 78 of 94

78. Question

Which of the following scheduling policy is well suited for a time-shared operating system?

Shortest job first
Round robin
First-c0m-first-serve
Elavator

Question 79 of 94

79. Question

The address sequence generated by tracing a particular program executing in a pure demand pagins system with 100 records per page, with 1 free main memory frame is recorded as follows. What is the number of page faults?
0100, 0200, 0430, 0499, 0510, 0530, 0560, 0120, 0220, 0240, 0260, 0320, 0370.

13
8
7
10

Question 80 of 94

80. Question

A computer system has 4 k word cache organized in a block-set-associative manner, with 4 blocks per set, 64 words per block. The number of bits in the SET and WORD fields of the main memory address format is

15.4
6.4
7.2
4.6

Question 81 of 94

81. Question

A computer installation has 1000 k of main memory. The jobs arrive and finish in the following sequence.
job 1 requiring 200 k arrives
job 2 requiring 350 k arrives
job 3 requiring 300 k arrives
job 1 finishes
job 4 requiring 120 k arrives
job 5 requiring 150 k arrives
job 6 requiring 80 k arrives
Among best fit and first fit, Which performs better for this sequence?

First fit
Best fit
Both perform the same
None of the above

Question 82 of 94

82. Question

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

LRU
FIFO
LFU
none of the above

Question 83 of 94

83. Question

Consider the following heap.
JOB 1 – 50
Free – 150
JOB 2 – 300
FREE – 350
JOB 3 – 600
The sequence of requests for blocks of size 300, 25, 125, 50 can be satisfied if we use

either-first fit or best fit policy
first fit but not best fit
best fit but not first fit
none of the above

Question 84 of 94

84. Question

This system is in a deadlock state. This remark is

true
false
impossible to determine
unpredictable

Question 85 of 94

85. Question

Which of the following is a safe sequence?

P0, P1, P2, P3
P1, P0, P3, P2
P2, P0, P1, P3
None of the above

Question 86 of 94

86. Question

A demand paging system, with page table held in registers, takes 5 ms to service a page fault if an empty page is available, or if the page to be replaced is not dirty. It takes 15 ms if the replaced page is dirty. Memory access time is 1 μ s and that the page to be replaced is dirty 60% of the time. What is the approximate maximum acceptable page fault rate to meet this access time requirement?

0.1%
1.0%
2.5%
0.01%

Question 87 of 94

87. Question

Consider a computer with 8 Mbytes of main memory and a 128 K cache. The cache block size is 4 K. It uses a direct mapping scheme for cache management. How many different main memory blocks can map onto a given physical cache block?

2048
256
64
None of the addresses

Question 88 of 94

88. Question

Which of the following applications are well suited for batch processing?

Process control
Video game control
Preparing pay bills of employees
Preparing mailing addresses

Question 89 of 94

89. Question

Locality of reference implies that the page reference being made by a process

will always be to the page used in the previous page reference.
is likely to be one of the pages used in the last few page references
will always to be one of the pages existing in memory.
will always leads to a page fault.

Question 90 of 94

90. Question

The correct matching for the following pairs
(A) Disk scheduling (1) Round robin
(B) Batch Processing (2) SCAN
(C) Time sharing (3) LIFO
(D) Interrupt Processing (4) FIFO
is

A-3, B-4, C-2 and D-1
A-4, B-3, C-2 and D-1
A-2, B-4, C-1 and D-3
A-2, B-1, C-4 and D-3

Question 91 of 94

91. Question

Thrashing

reduces page I/O
decreases the degree of multiprogramming
implies excessive page I/O
improves the system perfomance

Question 92 of 94

92. Question

Dirty bit for a page in a page table

helps avoid unnecessary writes on a paging device
helps maintain LRU information
allows only read on a page
none of the above

Question 93 of 94

93. Question

Each process P_i i= 1, 2, 3, . . . . 9 is coded as follows

repeat

p (mutex)

{ critical section }

V (mutex)

forever

The code for P10 is identical except that it uses V (mutex) instead of P (mutex). What is the largest number of processes that can be inside the critical section at any moment?

1
2
3
none of the above

Question 94 of 94

94. Question

When an interrupt occurs, an operating system

ignores the interrupt
always changes the state of the interrupted process after processing the interrupt
always resumes execution of the interrupted process after processing the interrupt
may change the state of the interrupted process to "blocked" and schedule another process.