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GATE 2022: Operating System Quiz-9

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Question 1

Consider a Demand Paging Environment Where system require 4 bytes to store integers and page size is of 256 bytes.
Assume the given code.
Int a [][] = new int a[200][250];
Int i=0, j=0;
While (i++ < 200)
{
while (j++< 250)
a [i][j]= 0;
}

What is the number of pages referenced from the system while executing the above code?

Question 2

Suppose system is using demand paging concept with 3 page frame. The next page references are 7, 6, 3, 4, 6, 4, 2, 3, 5. Then number of page faults if it uses different page replacement policy

Question 3

A demand paging system takes 250 time units to service a page fault and 450 time units to replace a dirty page. Memory access time is 10 time units. The probability of page faults is 0.7 .In case of a page fault, the probability of page being dirty is 0.06. The average access time is ________ time units (Upto 1 decimal place)

Question 4

A demand paging system has page fault service time as 125 time units if page is not dirty and 400 times units of page fault service time if it is a dirty page. Memory access time is 10 time units. The probability of a page fault is 0.3 .In case of page fault, the probability of page being dirty is P. It is observed that average access time is 50 time units. Then, the value of P is ______? [upto three decimal places]

Question 5

Consider the following reference string with four frames. The number of page-faults with optimal replacement under pure-Demand paging is

Ref. string: 1,2,3,4,5,3,4,1,6,7,8,7,8,9,7,8,8,9,5,4,5,4,2

Question 6

Consider a 2-dimensional array A[200][200]: Which stores integers, each of 4 bytes. The array is implemented in a pure demand paging memory system, which uses 256 Bytes page size. Consider the following segment to access the array:

Assume that array A should be stored in row major order on contiguous memory locations. And further assume that there is no any page available in main memory storing array element. How many page faults will occur to access array (only data) for executing above program segment?

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Sep 7GATE & PSU CS

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Megha GhoshMegha GhoshMember since Jul 2021
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