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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Q. In a paging system, it takes 30 ns to search translation Look-aside Buffer (TLB) and 90 ns to access the main memory. If the TLB hit ratio is 70%, the effective memory access time is:

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Q. Match the following w.r.t. Input/Output management:

List-l List-II
a. Device controller i. Extracts information from the controller register and store it in data buffer
b. Device driver ii. I/O scheduling
c. Interrupt handler iii. Performs data transfer
d. Kernel I/O subsystem iv. Processing of I/O request

Codes: a b c d

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Q. Which of the following scheduling algorithms may cause starvation?
a. First-come-first-served
b. Round Robin
c. Priority
d. Shortest process next
e. Shortest remaining time first

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Q. Distributed operating systems consist of:

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Q. Which of the following is incorrect for virtual memory

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Q. Consider following schedules involving two transactions:

S1: r1(X); r1(Y); r2(X); r2(Y); w2(Y); w1(X)
S2: r1(X); r2(X); r2(Y); w2(Y); r1(Y); w1(X)

Which of the following statement is true?

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Q. A memory management system has 64 pages with 512 bytes page size. Physical memory consists of 32 page frames. Number of bits required in logical and physical address are respectively:

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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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