Recent questions and answers in Operating System - GATE Overflow

+48 votes

5 answers

1

GATE1998-2.17, UGCNET-Dec2012-III-43
Consider $n$ processes sharing the CPU in a round-robin fashion. Assuming that each process switch takes $s$ seconds, what must be the quantum size $q$ such that the overhead resulting from process switching is minimized but at the same time each process is guaranteed to get its turn at ... $q \leq \frac{t-ns}{n+1}$ $q \geq \frac{t-ns}{n+1}$

answered 1 hour ago in Operating System by karsh (15 points) | 7.1k views

+14 votes

4 answers

2

TIFR2010-B-28
Consider the concurrent program: x: 1; cobegin x:= x + 3 || x := x + x + 2 coend Reading and writing of variables is atomic, but the evaluation of an expression is not atomic. The set of possible values of variable $x$ at the end of the execution of the program is: $\{4\}$ $\{8\}$ $\{4, 7, 10\}$ $\{4, 7, 8, 10\}$ $\{4, 7, 8\}$

answered 16 hours ago in Operating System by JashanArora Loyal (7.9k points) | 1k views

+14 votes

4 answers

3

GATE2007-83
A process, has been allocated $3$ page frames. Assume that none of the pages of the process are available in the memory initially. The process makes the following sequence of page references (reference string): $1, 2, 1, 3, 7, 4, 5, 6, 3, 1$ Least ... the above reference string, how many more page faults occur with LRU than with the optimal page replacement policy? $0$ $1$ $2$ $3$

answered 3 days ago in Operating System by Kushagra गुप्ता Loyal (5.6k points) | 1.7k views

+15 votes

5 answers

4

GATE2007-82
A process has been allocated $3$ page frames. Assume that none of the pages of the process are available in the memory initially. The process makes the following sequence of page references (reference string): $\mathbf{1, 2, 1, 3, 7, 4, 5, 6, 3, 1}$ If optimal page replacement policy is used, how many page faults occur for the above reference string? $7$ $8$ $9$ $10$

answered 3 days ago in Operating System by Kushagra गुप्ता Loyal (5.6k points) | 2.3k views

+1 vote

2 answers

5

ISRO2020-26
The operating system and the other processes are protected from being modified by an already running process because they run at different time instants and not in parallel they are in different logical addresses they use a protection algorithm in scheduler every address generated by the CPU is being checked against the relocation and limit parameters

answered 4 days ago in Operating System by JashanArora Loyal (7.9k points) | 221 views

+45 votes

4 answers

6

GATE2005-IT-81-b
A disk has $8$ equidistant tracks. The diameters of the innermost and outermost tracks are $1$ cm and $8$ cm respectively. The innermost track has a storage capacity of $10$ MB. If the disk has $20$ sectors per track and is currently at the end of the $5^{th}$ sector of the ... data starting from the sector $4$ of the outer-most track? $13.5 \ ms$ $10 \ ms$ $9.5 \ ms$ $20 \ ms$

answered 5 days ago in Operating System by Kushagra गुप्ता Loyal (5.6k points) | 4.3k views

+1 vote

2 answers

7

Self doubt
Virtual memory increases context switching overhead ? Why why not ?

answered Feb 18 in Operating System by smsubham Boss (12.5k points) | 85 views

+30 votes

6 answers

8

GATE2006-65
Consider three processes, all arriving at time zero, with total execution time of $10$, $20$ and $30$ units, respectively. Each process spends the first $\text{20%}$ of execution time doing I/O, the next $\text{70%}$ of time doing computation, and the last $\text{10%}$ of ... For what percentage of time does the CPU remain idle? $\text{0%}$ $\text{10.6%}$ $\text{30.0%}$ $\text{89.4%}$

answered Feb 12 in Operating System by Kushagra गुप्ता Loyal (5.6k points) | 5.8k views

0 votes

1 answer

9

TIFR2020-B-8
Jobs keep arriving at a processor. A job can have an associated time length as well as a priority tag. New jobs may arrive while some earlier jobs are running. Some jobs may keep running indefinitely. A starvation free job-scheduling policy ... following job-scheduling policies is starvation free? Round - robin Shortest job first Priority queuing Latest job first None of the others

answered Feb 11 in Operating System by Ashwani Kumar 2 Boss (16.9k points) | 39 views

0 votes

1 answer

10

Security
User x has found that s source code has a buffer overflow vulnerability caused by strcpy instruction. He then used strncpy in place of strcpy to prevent buffer overflow vulnerabilities Which of the following is true a. Buffer overflow attack will not occur in this source code b ... some extend since it do the bound check c. This will not make any change in the source code d. None of these

answered Feb 11 in Operating System by pranavthorkar (11 points) | 174 views

+12 votes

8 answers

11

GATE2019-17
The following C program is executed on a Unix/Linux system : #include<unistd.h> int main() { int i; for(i=0; i<10; i++) if(i%2 == 0) fork(); return 0; } The total number of child processes created is ________________ .

answered Feb 4 in Operating System by Ankit pipaliya (421 points) | 4.3k views

+23 votes

3 answers

12

GATE1999-2.11
Which of the following is/are advantage(s) of virtual memory? Faster access to memory on an average. Processes can be given protected address spaces. Linker can assign addresses independent of where the program will be loaded in physical memory. Program larger than the physical memory size can be run.

answered Feb 4 in Operating System by blackcloud Junior (655 points) | 3.5k views

0 votes

2 answers

13

PGT KVS 2016
S1 : a small page size causes large page tables. S2 : internal fragmentation is increased with small pages S3: I/O transfers are more efficient with large pages. a)S1 is true and S3 is false b)S1 and S2 are true c)S2 and S3 are true d)S1 is true and S2 is false

answered Jan 31 in Operating System by smsubham Boss (12.5k points) | 408 views

+40 votes

4 answers

14

GATE2001-2.22
Consider Peterson's algorithm for mutual exclusion between two concurrent processes i and j. The program executed by process is shown below. repeat flag[i] = true; turn = j; while (P) do no-op; Enter critical section, perform actions, then exit critical section Flag[i] = false; Perform other ... = i flag[j] = true and turn = j flag[i] = true and turn = j flag[i] = true and turn = i

answered Jan 30 in Operating System by iwasifirshad (129 points) | 5.1k views

+1 vote

4 answers

15

Andrew S. Tanenbaum (OS) Edition 4 Exercise 3 Question 24 (Page No. 256)
A machine has $48-bit$ virtual addresses and $32-bit$ physical addresses. Pages are $8\: KB.$ How many entries are needed for a single-level linear page table?

answered Jan 29 in Operating System by himanshukumarpatel (425 points) | 60 views

+64 votes

7 answers

16

GATE2012-32
Fetch_And_Add(X,i) is an atomic Read-Modify-Write instruction that reads the value of memory location $X$, increments it by the value $i$, and returns the old value of $X$. It is used in the pseudocode shown below to implement a busy-wait ... can take on a non-zero value when the lock is actually available works correctly but may starve some processes works correctly without starvation

answered Jan 29 in Operating System by iwasifirshad (129 points) | 10.8k views

+10 votes

6 answers

17

GATE2019-23
Consider three concurrent processes $P1$, $P2$ and $P3$ as shown below, which access a shared variable $D$ that has been initialized to $100$ ... maximum possible values of $D$ after the three processes have completed execution are $X$ and $Y$ respectively, then the value of $Y-X$ is ____

answered Jan 27 in Operating System by Kushagra गुप्ता Loyal (5.6k points) | 4.5k views

0 votes

2 answers

18

MadeEasy Subject Test: Operating System - Page Replacement
Why S1 is false??

answered Jan 27 in Operating System by Pankajmjx (33 points) | 82 views

+34 votes

9 answers

19

GATE2016-2-49
Consider a non-negative counting semaphore $S$. The operation $P(S)$ decrements $S$, and $V(S)$ increments $S$. During an execution, $20$ $P(S)$ operations and $12$ $V(S)$ operations are issued in some order. The largest initial value of $S$ for which at least one $P(S)$ operation will remain blocked is _______

answered Jan 27 in Operating System by JashanArora Loyal (7.9k points) | 5.1k views

0 votes

1 answer

20

synchronization reader's writer's problem.
int readers_count = 0; semaphore mutex = 1; // binary semaphore semaphore db = 1; // binary semaphore void reader() { while(TRUE) { x. down(mutex); //or wait(mutex) or P(mutex) readers_count = readers_count + 1; y. if(readers_count ... and writers are allowed in the database at the same time. c. There is possibility of deadlock. d. None of the above.

answered Jan 27 in Operating System by kunal goswami Junior (679 points) | 674 views

+35 votes

4 answers

21

GATE2015-2-49
Consider a typical disk that rotates at $15000$ rotations per minute (RPM) and has a transfer rate of $50 \times 10^6$ bytes/sec. If the average seek time of the disk is twice the average rotational delay and the controller's transfer time is $10$ times the disk transfer time, the average time (in milliseconds) to read or write a $512$-byte sector of the disk is _____

answered Jan 26 in Operating System by Kushagra गुप्ता Loyal (5.6k points) | 5.7k views

+10 votes

4 answers

22

GATE2019-41
Consider the following four processes with arrival times (in milliseconds) and their length of CPU bursts (in milliseconds) as shown below: ... Remaining Time First scheduling algorithm. If the average waiting time of the processes is $1$ millisecond, then the value of $Z$ is _____

answered Jan 26 in Operating System by Kushagra गुप्ता Loyal (5.6k points) | 3.9k views

+3 votes

4 answers

23

OS
Which of the following disk scheduling policies results in the minimum amount of head movement? (A) FCFS (B) Circular scan (C) Elevator

answered Jan 26 in Operating System by smsubham Boss (12.5k points) | 797 views

0 votes

1 answer

24

Galvin Edition 9 Exercise 10 Question 1 (Page No. 497)
Is disk scheduling, other than $FCFS$ scheduling, useful in a single-user environment ? Explain your answer.

answered Jan 26 in Operating System by smsubham Boss (12.5k points) | 33 views

+13 votes

2 answers

25

GATE1993-21
The following page addresses, in the given sequence, were generated by a program: $\text{1 2 3 4 1 3 5 2 1 5 4 3 2 3}$ This program is run on a demand paged virtual memory system, with main memory size equal to $4$ pages. Indicate the page references for which page faults occur for the following page replacement algorithms. LRU FIFO Assume that the main memory is initially empty

answered Jan 25 in Operating System by Kushagra गुप्ता Loyal (5.6k points) | 1k views

0 votes

1 answer

26

MadeEasy Subject Test 2019: Operating System - Threads

answered Jan 25 in Operating System by Anup dogrial (357 points) | 118 views

0 votes

1 answer

27

Andrew S. Tanenbaum (OS) Edition 4 Exercise 6 Question 22 (Page No. 467)
A system has two processes and three identical resources. Each process needs a maximum of two resources. Is deadlock possible? Explain your answer.

answered Jan 21 in Operating System by venkatesh pagadala Junior (737 points) | 35 views

0 votes

1 answer

28

Andrew S. Tanenbaum (OS) Edition 4 Exercise 6 Question 25 (Page No. 467)
The banker’s algorithm is being run in a system with $m$ resource classes and $n$ processes. In the limit of large $m$ and $n,$ the number of operations that must be performed to check a state for safety is proportional to $m^{a} n^{b}.$ What are the values of $a$ and $b?$

answered Jan 21 in Operating System by venkatesh pagadala Junior (737 points) | 32 views

+51 votes

3 answers

29

GATE2014-2-55
Consider the main memory system that consists of $8$ memory modules attached to the system bus, which is one word wide. When a write request is made, the bus is occupied for $100$ ... on the bus at any time. The maximum number of stores (of one word each) that can be initiated in $1$ millisecond is ________

answered Jan 21 in Operating System by JashanArora Loyal (7.9k points) | 7.6k views

+2 votes

2 answers

30

ISRO2020-57
The hardware implementation which provides mutual exclusion is Semaphores Test and set instructions Both options None of the options

answered Jan 20 in Operating System by smsubham Boss (12.5k points) | 550 views

+2 votes

1 answer

31

ISRO2020-30
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\ $ What are the minimum number of frames required to get a single page fault for the above sequence assuming LRU replacement strategy? $7$ $4$ $6$ $5$

answered Jan 19 in Operating System by arjun0001 (89 points) | 247 views

+72 votes

7 answers

32

GATE2005-72
Consider the following code fragment: if (fork() == 0) { a = a + 5; printf("%d, %p n", a, &a); } else { a = a - 5; printf ("%d, %p n", a,& a); } Let $u,v$ be the values printed by the parent process and $x,y$ be the values printed by the child process. Which one ... $u + 10 = x \text{ and } v = y$ $u + 10 = x \text{ and } v != y$

answered Jan 18 in Operating System by Shyam Nandan Kumar (51 points) | 10.2k views

+14 votes

4 answers

33

GATE2016-2-20
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? LRU (Least Recently Used) OPT (Optimal Page Replacement) MRU (Most Recently Used) FIFO (First In First Out)

answered Jan 17 in Operating System by swapnilbaviskar10 (55 points) | 2k views

+37 votes

4 answers

34

GATE2015-1-9
The following two functions $P1$ and $P2$ that share a variable $B$ with an initial value of $2$ ... $B$ can possibly take after the execution is______________________.

answered Jan 15 in Operating System by Vinit Gore (89 points) | 3.4k views

+1 vote

1 answer

35

UGCNET-dec2008-ii-22
If holes are half as large as processes, the fraction of memory wasted in holes is: (A) 2/3 (B) 1/2 (C) 1/3 (D) 1/5

answered Jan 14 in Operating System by abhinav kumar (165 points) | 211 views

+1 vote

3 answers

36

ISRO2020-25
What is compaction refers to a technique for overcoming internal fragmentation a paging technique a technique for overcoming external fragmentation a technique for compressing the data

answered Jan 13 in Operating System by Ashwani Kumar 2 Boss (16.9k points) | 164 views

+2 votes

1 answer

37

ISRO2020-31
Three CPU-bound tasks, with execution times of $15,12$ and $5$ time units respectively arrive at times $0,t$ and $8$ respectively. If the operating system implements a shortest remaining time first scheduling algorithm, what should be the value of $t$ to have $4$ context switches? Ignore the context switches at time $0$ and at the end. $0<t<3$ $t=0$ $t<=3$ $3<t<8$

answered Jan 13 in Operating System by STUDYGATE2019 (299 points) | 197 views

+1 vote

2 answers

38

ISRO2020-29
An aid to determine the deadlock occurrence is resource allocation graph starvation graph inversion graph none of the above

answered Jan 13 in Operating System by `JEET Boss (19.4k points) | 164 views

+1 vote

1 answer

39

ISRO2020-28
Dispatch latency is defined as the speed of dispatching a process from running to the ready state the time of dispatching a process from running to ready state and keeping the CPU idle the time to stop one process and start running another one none of these

answered Jan 13 in Operating System by `JEET Boss (19.4k points) | 136 views

+2 votes

1 answer

40

ISRO2020-27
Which of the following algorithms defines time quantum? shortest job scheduling algorithm round robin scheduling algorithm priority scheduling algorithm multilevel queue scheduling algorithm

answered Jan 13 in Operating System by `JEET Boss (19.4k points) | 123 views

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