CS/IT Gate Subject



Operating System GATE previous year questions with answer

Ques 40 Gate 2016 Set-2

In which one of the following page replacement algorithms it is possible for the page fault rate to increase even when the number of allocated frames increases?

A

LRU (Least Recently Used)

B

OPT (Optimal Page Replacement)

C

MRU (Most Recently Used)

D

FIFO (First In First Out)


(Page Replacement Algorithm) is the correct answer.

Ques 41 Gate 2016 Set-1

Consider a computer system with ten physical page frames. The system is provided with an access sequence a1, a2, ..., a20, a1, a2, ..., a20), where each ai number. The difference in the number of page faults between the last-in-first-out page replacement policy and the optimal page replacement policy is __________


(a) is the correct answer.

Ques 42 Gate 2016 Set-1

Consider a disk queue with requests for I/O to blocks on cylinders 47, 38, 121, 191, 87, 11, 92, 10. The C-LOOK scheduling algorithm is used. The head is initially at cylinder number 63, moving towards larger cylinder numbers on its servicing pass. The cylinders are numbered from 0 to 199. The total head movement (in number of cylinders) incurred while servicing these requests is______


(a) is the correct answer.

Ques 43 Gate 2016 Set-1

Consider a computer system with 40-bit virtual addressing and page size of sixteen kilobytes. If the computer system has a one-level page table per process and each page table entry requires 48 bits, then the size of the per-process page table is _________megabytes.


(a) is the correct answer.

Ques 44 Gate 2016 Set-1

Consider an arbitrary set of CPU-bound processes with unequal CPU burst lengths submitted at the same time to a computer system. Which one of the following process scheduling algorithms would minimize the average waiting time in the ready queue?

A

Shortest remaining time first

B

Round-robin with time quantum less than the shortest CPU burst

C

Uniform random

D

Highest priority first with priority proportional to CPU burst length


(Scheduling Algorithm) is the correct answer.

Ques 45 Gate 2015 Set-3

The maximum number of processes that can be in Ready state for a computer system with n CPUs is

A

n

B

n2

C

2n

D

Independent of n


(Process) is the correct answer.

Ques 46 Gate 2015 Set-1

Suppose the following disk request sequence (track numbers) for a disk with 100 tracks is given: 45, 20, 90, 10, 50, 60, 80, 25, 70. Assume that the initial position of the R/W head is on track 50. The additional distance that will be traversed by the R/W head when the Shortest Seek Time First (SSTF) algorithm is used compared to the SCAN (Elevator) algorithm (assuming that SCAN algorithm moves towards 100 when it starts execution) is _________ tracks


(a) is the correct answer.

Ques 47 Gate 2015 Set-1

The following two functions P1 and P2 that share a variable B with an initial value of 2 execute concurrently.

P1()
{
    C = B – 1;
    B = 2*C;
}

P2()
{
    D = 2 * B;
    B = D - 1;
}

The number of distinct values that B can possibly take after the execution is


(a) is the correct answer.

Ques 48 Gate 2014 Set-1

Which one of the following statements is FALSE?

A

The TLB performs an associative search in parallel on all its valid entries using the page number of the incoming virtual addresses.

B

If the virtual address of a word given by the CPU has a TLB hit, but the subsequent search for the word results in a cache miss, then the word will always be present in the main memory

C

The memory access time using a given inverted page table is always the same for all incoming virtual addresses.

D

In a system that uses hashed page tables, if two distinct virtual addresses V1 and V2 map to the same value while hashing, then the memory access time of these addresses will not be the same.


(1) is the correct answer.

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