Q. Consider a disk queue with I/O requests on the following cylinders in their arriving order:

6,10,12,54,97,73,128,15,44,110,34,45

The disk head is assumed to be at cylinder 23 and moving in the direction of decreasing number of cylinders. Total number of cylinders in the disk is 150. The disk head movement using SCAN-scheduling algorithm is:

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Q. Match the following for Unix rue system:

List-I                  List-II
a. Boot block     i. Information about file system,
free block list, free inode list etc.
b. Super block ii. Contains operating system files
as well as program and data files
created by users.
c. Inode block   iii. Contains boot program and
partition table.
d. Data block    iv. Contains a table for every file in
the file system. Attributes of files
are stored here.

Codes:
     a   b  c   d

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Q. Some of the criteria for calculation of priority of a process are:

a. Processor utilization by an individual process.
b. Weight assigned to a user or group of users.
c. Processor utilization by a user or group of processes.

In fair share scheduler, priority is calculated based on:

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Q. One of the disadvantages of user level threads compared to Kernel level threads is

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Q. Names of some of the Operating Systems are given below:

(a) MS-DOS
(b) XENIX
(c) OS/2

In the above list, following operating systems didn’t provide multiuser facility.

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Q. Consider a system with seven processes A through G and six resources R through W.
Resource ownership is as follows:

process A holds R and wants T
process B holds nothing but wants T
process C holds nothing but wants S
process D holds U and wants S & T
process E holds T and wants V
process F holds W and wants S
process G holds V and wants U

Is the system deadlocked ? If yes, ............. processes are deadlocked.

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Q. Suppose that the virtual Address space has eight pages and physical memory with four page frames. If LRU page replacement algorithm is used, .............. number of page faults occur with the reference string.

0 2 1 3 5 4 6 3 7 4 7 3 3 5 5 3 1 1 1 7 2 3 4 1

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Q. Consider a system having ‘m’ resources of the same type. These resources are shared by three processes P1, P2 and P3 which have peak demands of 2, 5 and 7 resources respectively. For what value of ‘m’ deadlock will not occur?

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Q. Five jobs A, B, C, D and E are waiting in Ready Queue. Their expected runtimes are 9, 6, 3, 5 and x respectively. All jobs entered in Ready queue at time zero. They must run in ............. order to minimize average response time if 3 < x < 5.

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Q. Consider three CPU intensive processes P1, P2, P3 which require 20, 10 and 30 units of time, arrive at times 1, 3 and 7 respectively. Suppose operating system is implementing Shortest Remaining Time first (pre-emptive scheduling) algorithm, then .............. context switches are required (suppose context switch at the beginning of Ready queue and at the end of Ready queue are not counted).

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Q. Consider a system which have ‘n’ number of processes and ‘m’ number of resource types. The time complexity of the safety algorithm, which checks whether a system is in safe state or not, is of the order of:

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Q. An operating system supports a paged virtual memory, using a central processor with a cycle time of one microsecond. It costs an additional one microsecond to access a page other than the current one. Pages have 1000 words, and the paging device is a drum that rotates at 3000 revolutions per minute and transfers one million words per second. Further, one percent of all instructions executed accessed a page other than the current page. The instruction that accessed another page, 80% accessed a page already in memory and when a new page was required, the replaced page was modified 50% of the time. What is the effective access time on this system, assuming that the system is running only one process and the processor is idle during drum transfers ?

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Q. Consider the following page reference string :

1, 2, 3, 4, 2, 1, 5, 6, 2, 1, 2, 3, 7, 6, 3, 2, 1, 2, 3, 6

Which of the following options, gives the correct number of page faults related to LRU, FIFO, and optimal page replacement algorithms respectively, assuming 05 page frames and all frames are initially empty ?

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Q. Consider a file currently consisting of 50 blocks. Assume that the file control block and the index block is already in memory. If a block is added at the end (and the block information to be added is stored in memory), then how many disk I/O operations are required for indexed (single-level) allocation strategy ?

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Q. Suppose that the number of instructions executed between page faults is directly proportional to the number of page frames allocated to a program. If the available memory is doubled, the mean interval between page faults is also doubled. Further, consider that a normal instruction takes one micro second, but if a page fault occurs, it takes 2001 micro seconds. If a program takes 60 sec to run, during which time it gets 15000 page faults, how long would it take to run if twice as much memory were available?

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Q. Consider a disk with 16384 bytes per track having a rotation time of 16 msec and average seek time of 40 msec. What is the time in msec to read a block of 1024 bytes from this disk?

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Q. Match the following with respect to various memory management algorithms :

List - I                                     List - II
(a) Demand paging                 (i) degree of multiprogramming
(b) Segmentation                     (ii) working set
(c) Dynamic partitions             (iii) supports user view of memory
(d) Fixed partitions                  (iv) compaction

Codes :
      (a)  (b)   (c)  (d)

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Q. Function of memory management unit is :

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Q. Consider a system with twelve magnetic tape drives and three processes P1, P2 and P3. Process P1 requires maximum ten tape drives, process P2 may need as many as four tape drives and P3 may need upto nine tape drives. Suppose that at time t1, process P1 is holding five tape drives, process P2 is holding two tape drives and process P3 is holding three tape drives. At time t1, system is in:

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Q. In an operating system, indivisibility of operation means :

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