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Review question of Protection and Security

Briefly explain how single, double, and circular buffering can be used to improve the performance of a process.

With single buffering, the operating system dedicates a buffer to a process. This allows the process to work on one block while theI/O system reads another block into the buffer.

With double buffering, the operating system dedicates two buffers to a process. The process can then empty one buffer while the I/Osystem fills the other. This allows the process to process data as fast as the I/O system can read it in.

Why is the average search time to find a record in a file less for an indexed sequential file than for a sequential file?

With a sequential file, the records are stored in order of a particular key, but searching requires going through all of therecords sequentially until a match is found. In an indexed sequential file, the index contains pointers to every K records in the file. For a file with Nrecords, searching for a record with a particular key requires searching only the N/K entries in the index, and then the K records in that section of thefile. Depending on the size of K, this can be considerably less than sequentially searching through all N entries.

Briefly describe the four categories of information stored in a file directory. give an example of an item from each category, along with a oneSentence description.

  • Basic information is used to identify the file and includes the file name and type.
  • Address information is used to find the file on disk and includes the address and size of the file.
  • Access control information is used to provide sharing and protection and includes the owner and related access information.
  • Usage information is used for accounting and includes such items as the date of creation and last modification.

Problems

Perform the same type of analysis as that of table 11.2 for the following sequence of disk track requests: 27, 129, 110, 186, 147, 41, 10, 64,120. assume that the disk head is initially positioned over track 100 and is moving in the direction of decreasing track number. do the same analysis, butNow assume that the disk head is moving in the direction of increasing track number.

Answer:

FIFO SSTF SCAN C-SCAN
Next track accessed Number of tracks traversed Next track accessed Number of tracks traversed Next track accessed Number of tracks traversed Next track accessed Number of tracks traversed
27 73 110 10 64 36 64 36
129 102 120 10 41 23 41 23
110 19 129 9 27 14 27 14
186 76 147 18 10 17 10 17
147 39 186 39 110 100 186 176
41 106 64 122 120 10 147 39
10 31 41 23 129 9 129 18
64 54 27 14 147 18 120 9
120 56 10 17 186 39 110 10
Average 61.8 Average 29.1 Average 29.6 Average 38

If the disk head is initially moving in the direction of increasing track number, the results change for only scan and c-scan:

SCAN C-SCAN
Next track accessed Number of tracks traversed Next track accessed Number of tracks traversed
110 10 110 10
120 10 120 10
129 9 129 9
147 18 147 18
186 39 186 39
64 122 10 176
41 23 27 17
27 14 41 14
10 17 64 23
Average 29.1 Average 35.1

Consider the disk system described in Problem 11.9 and assume the disk rotates at 360 rpm. A processor reads one sector from thedisk using interrupt-driven I/O, with one interrupt per byte. If it takes 2.5 μs to process each interrupt, what percentage of time will the processor spendhandling I/O (disregard seek time)? Repeat using DMA, and assume one interrupt per sector.

Questions & Answers

Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
hi
Loga
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Source:  OpenStax, Operating systems. OpenStax CNX. Aug 13, 2009 Download for free at http://cnx.org/content/col10785/1.2
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