Q. Which methods are utilized to control the access to an object in multi-threaded programming?

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Q. Various storage devices used by an operating system can be arranged as follows in increasing order of accessing speed:

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Q. How many disk blocks are required to keep list of free disk blocks in a 16 GB hard disk with 1 kB block size using linked list of free disk blocks? Assume that the disk block number is stored in 32 bits.

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Q. Consider an imaginary disk with 40 cylinders. A request come to read a block on cylinder 11. While the seek to cylinder 11 is in progress, new requests come in for cylinders 1, 36, 16, 34, 9 and 12 in that order. The number of arm motions using shortest seek first algorithm is

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Q. An operating system has 13 tape drives. There are three processes PI, P2 & P3.1 Maximum requirement of PI is 11 tape drives, P2 is 5 tape drives and P3 is 8 tape drives. Currently, PI is allocated 6 tape drives, P2 is allocated 3 tape drives and P3 is allocated 2 tape drives. Which of the following sequences represent a safe state?

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Q. Monitor is an Interprocess Communication (IPC) technique which can be described as

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Q. A disk drive has 100 cylinders, numbered 0 to 99. Disk requests come to the disk driver for cylinders 12,26,24,4,42,8 and 50 in that order. The driver is currently serving a request at cylinder 24- A seek takes 6 msec per cylinder moved. How much seek time is needed for shortest seek time first (SSTF) algorithm ?

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Q. Let Pi and Pj be two processes, R be the set of variables read from memory, and W be the set variables written to memory. For the concurrent execution of two processes Pi and Pj, which of the following conditions is not true?

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Q. A LRU page replacement is used with four page frames and eight pages. How many page faults will occur with the reference string 0172327103 if the four frames are initially empty?

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Q. Match the following for operating system techniques with the most appropriate advantage :

List – I List – II

(a) Spooling (i) Allows several jobs in memory to improve CPU utilization

(b) Multiprogramming (ii) Access to shared resources among geographically dispersed computers in a transparent way

(c) Time sharing (iii) Overlapping I/O and computations

(d) Distributed computing (iv) Allows many users to share a computer simultaneously by switching processor frequently

Codes:
a b c d

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Q. Which of the following statements is not true for Multi-Level Feedback Queue processor scheduling algorithm?

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Q. What is the most appropriate function of Memory Management Unit (MMU)?

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Q. In ___________ allocation method for disk block allocation in a file system, insertion and deletion of blocks in a file is easy.

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Q. Consider a program that consists of 8 pages (from 0 to 7) and we have 4 page frames in the physical memory
for the pages. The page reference string is :
1 2 3 2 5 6 3 4 6 3 7 3 1 5 3 6 3 4 2 4 3 4 5 1
The number of page faults in LRU and optimal page replacement algorithms are respectively (without including initial page faults to fill available page frames with, pages) :

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Q. Which of the following statements is not true about disk-arm scheduling algorithms?

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Q. Consider the reference string 0 1 2 3 0 1 4 0 1 2 3 4 If FIFO page replacement algorithm is used, then the number of page faults with three page frames and four page frames are .......... and ........... respectively.

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Q. Suppose there are four processes in execution with 12 instances of a Resource R in a system. The maximum need of each process and current allocation are given below:
Process Max. Need Current Allocation
P1 8 3
P2 9 4
P3 5 2
P4 3 1

With reference to current allocation, is system safe? If so, what is the safe sequence?

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Q. If the Disk head is located initially at track 32, find the number of disk moves required with FCFS scheduling criteria if the disk queue of I/O blocks requests are: 98, 37, 14, 124, 65, 67

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Q. A scheduling Algorithm assigns priority proportional to the waiting time of a process. Every process starts with priority zero (lowest priority). The scheduler re-evaluates the process priority for every 'T' time units and decides next process to be scheduled. If the process have no I/O operations and all arrive at time zero, then the scheduler implements .............. criteria.

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Q. There are three processes P1, P2 and P3 sharing a semaphore for synchronising a variable. Initial value of semaphore is one. Assume that negative value of semaphore tells us how many processes are waiting in queue. Processes access the semaphore in following order:

(a) P2 needs to access
(b) P1 needs to access
(c) P3 needs to access
(d) P2 exits critical section
(e) Pi exits critical section

The final value of semaphore will be:

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