Recent questions and answers in Operating System

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1

Threads
Consider the following statements: S1 : Multiprogramming is used to increase CPU utilization, while time-sharing is used to increase CPU responsiveness in interacting with user. S2 : If a user-level thread is blocked for I/O operation, then kernel of ... several userlevel threads to be assigned to different processors in a multi-processor computer system. Which of the following is true?

answered 7 minutes ago in Operating System by blackcloud (141 points) | 128 views

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2

Made Easy Test Series:OS
Consider the following solution for critical section problem with 'n' processes P0,P1,P2,......P(n-1).For all i,number[i] is an integer array initialized to zero, and for all j,choosing[j] is a binary array initialized to false. CODE FOR Pi : Repeat { ... only. b)S1 and S2 only. c)S2 and S3 only. d)S1 , S2 and S3 (please anyone elaborate this solution.thanks in advance)

answered 52 minutes ago in Operating System by srestha Veteran (116k points) | 49 views

+1 vote

1 answer

3

Interrupt Service Routing ( Applied course Mock 3)
Consider a process P1 that is executing on a Linux-like OS on a single core system. When P1 is executing, a disk interrupt occurs, causing P1 to go to kernel mode to service that interrupt. The interrupt delivers all the disk blocks that unblock ... is ready P1 is ready and P2 is running P1 is running and P2 is ready P1 is blocked and P2 is ready

answered 9 hours ago in Operating System by Applied Course Junior (653 points) | 131 views

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4

Andrew S. Tanenbaum (OS) Edition 4 Exercise 2 Question 1 (Page No. 174)
In Fig. $2-2$, three process states are shown. In theory, with three states, there could be six transitions, two out of each state. However, only four transitions are shown. Are there any circumstances in which either or both of the missing transitions might occur?

asked 9 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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5

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 35 (Page No. 83 - 84)
If you have a personal UNIX-like system (Linux, MINIX $3$, FreeBSD, etc.) available that you can safely crash and reboot, write a shell script that attempts to create an unlimited number of child ... system administrator. The consequences will be instantly obvious so you are likely to be caught and sanctions may follow.

asked 9 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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6

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 36 (Page No. 84)
Examine and try to interpret the contents of a UNIX-like or Windows directory with a tool like the UNIX od program. (Hint: How you do this will depend upon what the OS allows. One trick that may work is ... with one operating system and then read the raw device data using a different operating system that allows such access.)

asked 9 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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7

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 34 (Page No. 83)
Write a shell that is similar to Fig. $1-19$ but contains enough code that it actually works so you can test it. You might also add some features such as redirection of input and output, pipes, and background jobs.

asked 9 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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8

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 33 (Page No. 83)
Here are some questions for practicing unit conversions: How long is a nanoyear in seconds? Micrometers are often called microns. How long is a megamicron? How many bytes are there in a $1$-PB memory? The mass of the earth is $6000$ yottagrams. What is that in kilograms?

asked 9 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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9

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 32 (Page No. 83)
Virtual machines have become very popular for a variety of reasons. Nevertheless, they have some downsides. Name one.

asked 9 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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10

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 31 (Page No. 83)
Explain how separation of policy and mechanism aids in building microkernel-based operating systems.

asked 9 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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11

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 30 (Page No. 83)
A portable operating system is one that can be ported from one system architecture to another without any modification. Explain why it is infeasible to build an operating system that is completely portable. Describe two high-level layers that you will have in designing an operating system that is highly portable.

asked 9 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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12

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 29 (Page No. 83)
Figure $1-23$ shows that a number of UNIX system calls have no Win32 API equivalents. For each of the calls listed as having no Win32 equivalent, what are the consequences for a programmer of converting a UNIX program to run under Windows?

asked 9 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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13

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 28 (Page No. 83)
To a programmer, a system call looks like any other call to a library procedure. Is it important that a programmer know which library procedures result in system calls? Under what circumstances and why?

asked 9 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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14

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 27 (Page No. 83)
Modern operating systems decouple a process address space from the machine’s physical memory. List two advantages of this design.

asked 9 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 2 views

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15

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 26 (Page No. 83)
In the example given in Fig. $1-17$, the library procedure is called read and the system call itself is called read. Is it essential that both of these have the same name? If not, which one is more important?

asked 9 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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16

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 25 (Page No. 83)
What is the essential difference between a block special file and a character special file?

asked 9 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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17

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 24 (Page No. 83)
Suppose that a $10$-MB file is stored on a disk on the same track (track $50$) in consecutive sectors. The disk arm is currently situated over track number $100$. How long will it take to retrieve this file from the disk? ... the file is stored to rotate under the head. Also, assume that reading occurs at a rate of $200$ MB/s.

asked 9 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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18

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 23 (Page No. 82 - 83)
A file whose file descriptor is fd contains the following sequence of bytes$: 3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5.$ The following system calls are made: lseek(fd, $3$, SEEK SET); read(fd, &buffer, $4$); where the lseek call makes a seek to byte $3$ of the file. What does buffer contain after the read has completed?

asked 10 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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19

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 22 (Page No. 82)
Can the count = write(fd, buffer, nbytes); call return any value in count other than nbytes? If so, why?

asked 10 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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20

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 21 (Page No. 82)
What type of multiplexing (time, space, or both) can be used for sharing the following resources: CPU, memory, disk, network card, printer, keyboard, and display?

asked 10 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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21

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 20 (Page No. 82)
For each of the following system calls, give a condition that causes it to fail: fork, exec, and unlink.

asked 10 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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22

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 19 (Page No. 82)
Is there any reason why you might want to mount a file system on a nonempty directory? If so, what is it?

asked 10 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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23

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 18 (Page No. 82)
Why is the process table needed in a timesharing system? Is it also needed in personal computer systems running UNIX or Windows with a single user?

asked 10 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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24

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 17 (Page No. 82)
What is a trap instruction? Explain its use in operating systems.

asked 10 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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25

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 16 (Page No. 82)
When a user program makes a system call to read or write a disk file, it provides an indication of which file it wants, a pointer to the data buffer, and the count. Control is then transferred to the operating ... What about the case of writing to the disk? Need the caller be blocked awaiting completion of the disk transfer?

asked 10 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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26

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 15 (Page No. 82)
Consider a computer system that has cache memory, main memory (RAM) and disk, and an operating system that uses virtual memory. It takes $1$ nsec to access a word from the cache, $10$ nsec to access a word from the RAM, and ... and main memory hit rate (after a cache miss) is $99\%$, what is the average time to access a word?

asked 10 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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27

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 14 (Page No. 82)
A computer has a pipeline with four stages. Each stage takes the same time to do its work, namely, $1$ nsec. How many instructions per second can this machine execute?

asked 10 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 2 views

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28

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 13 (Page No. 82)
Consider a system that has two CPUs, each CPU having two threads (hyperthreading). Suppose three programs, $P0, P1,$ and $P2$, are started with run times of $5, 10$ and $20$ msec, respectively. How long will it ... all three programs are $100\%$ CPU bound, do not block during execution, and do not change CPUs once assigned.

asked 10 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 2 views

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29

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 12 (Page No. 82)
Which of the following instructions should be allowed only in kernel mode? Disable all interrupts. Read the time-of-day clock. Set the time-of-day clock. Change the memory map

asked 10 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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30

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 11 (Page No. 81)
A $255$-GB disk has $65,536$ cylinders with $255$ sectors per track and $512$ bytes per sector. How many platters and heads does this disk have? Assuming an average cylinder seek time of $11$ ms, average rotational delay ... reading rate of $100$ MB/sec, calculate the average time it will take to read $400$ KB from one sector.

asked 10 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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31

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 10 (Page No. 81)
What is the difference between kernel and user mode? Explain how having two distinct modes aids in designing an operating system.

asked 10 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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32

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 9 (Page No. 81)
There are several design goals in building an operating system, for example, resource utilization, timeliness, robustness, and so on. Give an example of two design goals that may contradict one another.

asked 10 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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33

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 8 (Page No. 81)
One reason GUIs were initially slow to be adopted was the cost of the hardware needed to support them. How much video RAM is needed to support a $25-\text{line}\times\: 80-\text{row}$ character monochrome text screen? How much for a ... $ prices $(\$5/KB)?$ How much is it now?

asked 10 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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34

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 7 (Page No. 81)
The family-of-computers idea was introduced in the $1960s$ with the IBM System$/360$ mainframes. Is this idea now dead as a doornail or does it live on?

asked 10 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

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35

Andrew S. Tanenbaum (OS) Edition 4 Exercise 1 Question 6 (Page No. 81)
Instructions related to accessing I/O devices are typically privileged instructions, that is, they can be executed in kernel mode but not in user mode. Give a reason why these instructions are privileged.

asked 10 hours ago in Operating System by Lakshman Patel RJIT Veteran (51.5k points) | 1 view

+4 votes

4 answers

36

ISRO2016-48
Determine the number of page faults when references to pages occur in the following order: 1, 2, 4, 5, 2, 1, 2, 4 Assume that the main memory can accommodate 3 pages and the main memory already has the pages 1 and 2, with page one having brought earlier than page 2. (LRU page replacement algorithm is used) 3 5 4 None of these

answered 11 hours ago in Operating System by Shreyshi Pandey (45 points) | 3.6k views

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4 answers

37

UGCNET-AUG2016-II-37
Suppose that the virtual Address space has eight pages and physical memory with four page frames. If $LRU$ page replacement algorithm is used, ______ number of page faults occur with the reference string. 0 2 1 3 5 4 6 3 7 4 7 3 3 5 5 3 1 1 1 7 2 3 4 1 $11$ $12$ $10$ $9$

answered 11 hours ago in Operating System by Shreyshi Pandey (45 points) | 344 views

+1 vote

4 answers

38

UGCNET-June-2019-II-43
Consider that a process has been allocated $3$ frames and has a sequence of page referencing as $1, 2, 1, 3, 7, 4, 5, 6, 3, 1$. What shall be the difference in page faults for the above string using the algorithms of LRU and optimal page replacement for referencing the string? $2$ $0$ $1$ $3$

answered 12 hours ago in Operating System by Shreyshi Pandey (45 points) | 100 views

+1 vote

4 answers

39

UGCNET-June-2019-II-41
Consider a disk system with $100$ cylinders. The requests to access the cylinders occur in the following sequences: $4, 34, 10, 7, 19, 73, 2, 15, 6, 20$ Assuming that the head is currently at cylinder $50$, what is the time taken to satisfy all requests ... from the cylinder to adjacent one and the shortest seek time first policy is used? $357$ ms $238$ ms $276$ ms $119$ ms

answered 12 hours ago in Operating System by Shreyshi Pandey (45 points) | 116 views

+2 votes

4 answers

40

UGCNET-June-2019-II-42
Match List-I with List-II: ... below: a-i; b-ii; c-iii; d-iv a-iii; b-i; c-iv; d-ii a-ii; b-i; c-iv; d-iii a-ii; b-iv; c-iii; d-i

answered 12 hours ago in Operating System by Shreyshi Pandey (45 points) | 115 views

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