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1. [20 points, 1 each] true or false, circle t or f.

a. A binary semaphore takes on numerical values 0 and 1 only.

b. An atomic operation is a machine instruction or a sequence of instructions

that must be executed to completion without interruption.

c. Deadlock is a situation in which two or more processes (or threads) are waiting for an event that will occur in the future

d. Starvation is a situation in which a process is denied access to a resource

because of the competitive activity of other, possibly unrelated, processes.

e. While a process is blocked on a semaphore's queue, it is engaged in busy waiting.

f. Circular waiting is a necessary condition for deadlock, but not a sufficient

condition a condition for the deadlock to occur.

g. Mutual exclusion can be enforced with a general semaphore whose initial value is greater than 1

h. External fragmentation can occur in a paged virtual memory system.

i. External fragmentation can be prevented (almost completely) by frequent use of compaction, but the cost would be too high for most systems.

j. A page frame is a portion of main memory.

k. Once a virtual memory page is locked into main memory, it cannot be written to the disk.

l. Pages that are shared between two or more processes can never be swapped out to the disk.

m. The allocated portions of memory using a buddy system are all the same size.

n. Demand paging requires the programmer to take specific action to force the

operating system to load a particular virtual memory page.

o. Prepaging is one possibility for the fetch policy in a virtual memory system.

p. The resident set of a process can be changed in response to actions by other processes.

q. The working set of a process can be changed in response to actions by other processes.

r. The translation lookaside buffer is a software data structure that supports he virtual memory address translation operation.

s. In a symmetric multiprocessor, threads can always be run on any processor.

t. Thrashing will never be a problem if the system has 1 GB of real memory.

2. [20 points, 5 each] short answers and simple diagrams.

(a) Define the resident set of a process.

(b) Define the working set of a process.

(c) What problems could occur if virtual memory pages are always allocated in groups of four?

(d) What information is used by the Least Recently Used page replacement policy, and how does this compare to the information used by the various Clock algorithms?

3. [20 points, 5 each] short answers and simple diagrams.

(a) In terms of memory allocation, what is a reference counter? Why is it needed?

(b) Explain why, or why not, internal fragmentation can be a problem when using the best fit algorithm for memory allocation.

(c) One of the options in a mainframe OS is to limit the number of jobs (processes) currently in the system. What are some of the benefits of this capability?

(d) In what circumstances of virtual memory is the placement policy an important issue?

4. [20 points, 5 each] short answers.

(a) What are four general characteristics of processor scheduling policies?

(b) Define Turnaround Time and Normalized Turnaround Time. Why are these useful for measuring the performance of a scheduling algorithm?

(c) What would be the effect of a large number of page faults by a process on that process's page allocation on a nonpreemptive operating system?

(d) What are four actions or decisions that a preemptive virtual memory operating system would make at the end of a time quantum (in response to a timer interrupt)?

5. [20 points]

This function is proposed for use in an operating system, with the definitions of

Process, Process_Set and other functions given elsewhere.

Process next_process(Process_Set available_processes) {

Process_Set A = highest_valuation(available_processes); /* priority ranking */

Process_Set B = earliest(A); /* actual arrival time */

Process c = random_selection(B); /* tie-breaker */

return c; /* run this process next */

}

(a) [5] Explain why this function could lead to processor starvation among the available processes.

(b) [5] Suppose one of the criteria used by the highest_valuation function is the process's fraction of virtual memory pages currently in main memory. Explain why this is not a good idea.

(c) [10] Define a version of the highest_valuation function (in the same style, but with some more descriptive comments) for the Shortest Process Next scheduling policy. Describe the data requirements and how this data is obtained.

Questions & Answers

find the 15th term of the geometric sequince whose first is 18 and last term of 387
Jerwin Reply
I know this work
salma
The given of f(x=x-2. then what is the value of this f(3) 5f(x+1)
virgelyn Reply
hmm well what is the answer
Abhi
how do they get the third part x = (32)5/4
kinnecy Reply
can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
ninjadapaul
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
ninjadapaul
I don't understand what the A with approx sign and the boxed x mean
ninjadapaul
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
ninjadapaul
oops. ignore that.
ninjadapaul
so you not have an equal sign anywhere in the original equation?
ninjadapaul
hmm
Abhi
is it a question of log
Abhi
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Abhi
I rally confuse this number And equations too I need exactly help
salma
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salma
Commplementary angles
Idrissa Reply
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Sherica
im all ears I need to learn
Sherica
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Tamia
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Uday
hi
salma
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
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Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Al
y=10×
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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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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