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Answer questions 1, 2, 3, 4 and any one other question of yourchoice.

Operating system is the key foundation software that set up thecomputer to run other advantage software. As a perspective

software engineer that will e designing application software thatwill run!operate in computer platform, e"plain in detail andspecificity the importance of operating system to you.

2. #numerate and e"plain in detail common techniques used insoftware engineering to create the illusion of quick responseinitiation of a software program installed in a computer system. $oushould give concrete or specific e"amples of the operating initiationmechanics of software which will create perception of quickresponse despite the fact that normal amounts of time to complete

loading up %front key essential files remain the same.3. &hat key parts of operating system help load software programinto a computer system and ensures that the program runssmoothly' (lease e"plain this process in your own words, as well aseing very specific in your response. )int* the answer to thisquestion is not presented as a +lock* in your te"took or any oneparticular reading material. his technique was e"plained in classusing internet rowser as an e"ample.

4. #fficient use of the processor and -!O facilities has een a keyconcern of software engineers for the past 3 years. /iscuss in yourown words, how processor and -nput!Out facilities can efficiently emanaged to yield ma"imum efficiency and output without si0erestrictions in the program development process.

An operating system is the program that, after eing initially loadedinto the computer y a oot program, manages all the otherprograms in a computer. he other programs are called applications

or application programs. he application programs make use of theoperating system y making requests for services through a definedapplication program interface A(-. -n addition, users can interactdirectly with the operating system through a user interface such ascommand language or a graphical user interface -.

An operating system performs these services for applications

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-n a multitasking operating system where multiple programscan e running at the same time, the operating system determineswhich applications should run in what order and how much timeshould e allowed for each application efore giving anotherapplication

-t manages the sharing of internal memory among multipleapplications.

-t handles input and output to and from attached hardwaredevices, such as hard disks, printers, and dial%up ports

-t sends messages to each application or interactive user or toa system operator aout the status of operation and any errors thatmay have occurred.

-t can offload the management of what are called atch

5os for e"ample, printing so that the initiating application is freedfrom this work

On computers that can provide parallel processing, anoperating system can manage how to divide the program so that itruns on more than one processor at a time

6. ni%processor 7cheduling is very crucial as an operating systemmust assign computer resources e.g. e"ecution time, etc amongcompeting needs of multiple processes. 8riefly discuss in your ownwords three main types of processor scheduling with specifice"amples of each type. $ou may use schematics to support youre"planation.

9. -nput!Out management and disk scheduling were e"tensivelydiscussed in class this quarter. #laorate on forms of -!O devices,O!7 design issues familiar to you, -!O uffering, :A/ and diskcache. $ou can see that this question is ;open%ended

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=. #"plain in detail the differences etween a field and a record,and a file and a dataase.

>. ?ile organi0ation to a software engineer is very important.herefore, list and define five file organi0ations. 7econdly, riefly

discuss the functions of O!7 :egistry. (lease provide youre"planations in your own words.

Pile

It's the simplest possible organization: the data are collected in the file in the order in

which they arrive, and it's not even required that the records have a common format

across the file (different fields/sizes, same fields in different orders, etc.are possible.

!his implies that each record/field must be self"describing. #espite the obvious

storage efficiency and the easy update, it's quite clear that this $$structure'' is not suitedfor easy data retireval, since retrieving a datum basically requires detailed analysis of

the file content. It ma%es sense only as temporary storage for data to be later

structured in some way.

Sequential

!his is the most common structure for large files that are typically processed in their

entirety, and it's at the heart of the more comple& schemes. In this scheme, all the

records have the same size and the same field format, with the fields having fi&ed size

as well. !he records are sorted in the file according to the content of a field of a scalartype, called $$%ey''. !he %ey must identify uniquely a records, hence different record

have diferent %eys. !his organization is well suited for batch processing of the entire

file, without adding or deleting items: this %ind of operation can ta%e advantage of the

fi&ed size of records and file moreover, this organization is easily stored both on dis%

and tape. !he %ey ordering, along with the fi&ed record size, ma%es this organization

amenable to dicotomic search owever, adding and deleting records to this %ind of

file is a tric%y process: the logical sequence of records tipycally matches their physical

layout on the media storage, so to ease file navigation, hence adding a record and

maintaining the %ey order requires a reorganization of the whole file. !he usual

solution is to ma%e use of a $$log file'' (also called $$transaction file'', structured as apile, to perform this %ind of modification, and periodically perform a batch update on

the master file.

http://www.cim.mcgill.ca/~franco/OpSys-304-427/lecture-notes/footnode.html#790

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Indexed sequential

)n inde& file can be used to effectively overcome the above mentioned problem, and

to speed up the %ey search as well. !he simplest inde&ing structure is the single"level

one: a file whose records are pairs %ey"pointer, where the pointer is the position in the

data file of the record with the given %ey. *nly a subset of data records, evenly spacedalong the data file, are inde&ed, so to mar% intervals of data records.

) %ey search then proceeds as follows: the search %ey is compared with the inde&

ones to find the highest inde& %ey preceding the search one, and a linear search is

performed from the record the inde& %ey points onward, until the search %ey is

matched or until the record pointed by the ne&t inde& entry is reached. In spite of the

double file access (inde& + data needed by this %ind of search, the decrease in access

time with respect to a sequential file is significant.

onsider, for e&ample, the case of simple linear search on a file with -, records.ith the sequential organization, an average of 0 %ey comparisons are necessary

(assuming uniformly distributed search %ey among the data ones. owever, using

and evenly spaced inde& with - entries, the number of comparisons is reduced to 0

in the inde& file plus 0 in the data file: a 0:- reduction in the number of operations.

!his scheme can obviously be hyerarchically e&tended: an inde& is a sequential file in

itself, amenable to be inde&ed in turn by a second"level inde&, and so on, thus

e&ploiting more and more the hyerarchical decomposition of the searches to decrease

the access time. *bviously, if the layering of inde&es is pushed too far, a point is

reached when the advantages of inde&ing are hampered by the increased storage costs,

and by the inde& access times as well.

Indexed

hy using a single inde& for a certain %ey field of a data record1 Inde&es can be

obviously built for each field that uniquely identifies a record (or set of records within

the file, and whose type is amenable to ordering. 2ultiple inde&es hence provide a

high degree of fle&ibility for accessing the data via search on various attributes this

organization also allows the use of variable length records (containing different

fields.

It should be noted that when multiple inde&es are are used the concept of sequentiality

of the records within the file is useless: each attribute (field used to construct an

inde& typically imposes an ordering of its own. 3or this very reason is typicaly not

possible to use the $$sparse'' (or $$spaced'' type of inde&ing previously described. !wo

types of inde&es are usually found in the applications: the e&haustive type, which

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contains an entry for each record in the main file, in the order given by the inde&ed

%ey, and the partial type, which contain an entry for all those records that contain the

chosen %ey field (for variable records only.

Hashed

)s with sequential or inde&ed files, a %ey field is required for this organization, as

well as fi&ed record length. owever, no e&plicit ordering in the %eys is used for the

hash search, other than the one implicitly determined by a hash function.

he registry is a dataase of all configuration and operating information for the

operating system.

Warning* #diting the registry is considered to e a very dangerous process, and

could (if done incorrectly)cause the operating system to fail and the computer to not

start. 8e very, very careful and follow @icrosofts recommendations for acking up and

eing ale to restore the registry, and also to know e"actly what you are doing. his is

complicated y the fact that the registry editing tools do not give you a chance to

confirm your actions % they happen immediately % so you get no second chances.

Thanks for taking SOF 560. You have made the course enoya!leand re"arding for all of us. #ood luck to all of you$