حلول اسئله الامتحانات

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    sandy.h
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    حلول اسئله الامتحانات

    مُساهمة من طرف sandy.h في الأحد 26 أبريل 2009 - 17:52

    السلام عليكم ورحمه الله

    دلوقتي انا عندي اقترااح بالنسبه لامتحانات السنين اللي فاتت
    كل اللي يعرف اجابه سؤال يجي يحط السؤال باجابته هنا
    لو الفكره عجبتكوا يا ريت نبدأ فيها
    انا عن نفسي هبدأ من المشاركه الجايه هحط الاسئله اللي اعرف اجابتها

    بالتوفيق Smile


    سلام


    عدل سابقا من قبل sandy.h في الأحد 17 مايو 2009 - 12:10 عدل 1 مرات




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    مُساهمة من طرف sandy.h في الأحد 26 أبريل 2009 - 17:54

    Q:explain first-fit , best-fit and worst-fit method oa allocating space for
    contiguous file ??

    Answer:
    First-fit: allocate the first space that is big enough;
    Best-fit: allocate the smallest space that is big enough;
    Worst-fit: allocate the largest space.

    Q:What problems could occur if a system allowed a file system to be
    mounted simultaneously at more than one location?

    Answer:
    There would be multiple paths to the same file, which could
    confuse users or encourage mistakes (deleting a file with one path
    deletes the file in all the other paths).



    Q:Consider a system that supports the strategies of contiguous, linked,
    and indexed allocation.What criteria should be used in decidingwhich
    strategy is best utilized for a particular file?

    Answer:
    Contiguous—if file is usually accessed sequentially, if file is
    relatively small.
    Linked—if file is large and usually accessed sequentially.
    Indexed—if file is large and usually accessed randomly.

    Q:How do caches help improve performance? Why do systems not use
    more or larger caches if they are so useful?

    Answer:
    Caches allow components of differing speeds to communicate
    more efficiently by storing data from the slower device, temporarily,
    in a faster device (the cache). Caches are, almost by definition, more
    expensive than the device they are caching for, so increasing the number
    or size of caches would increase system cost.

    Q:(midterm--2006--)
    Some systems automatically delete all user files when a user logs off or
    a job terminates, unless the user explicitly requests that they be kept;
    other systems keep all files unless the user explicitly deletes them.
    Discuss the relative merits of each approach.

    Answer:
    Deleting all files not specifically saved by the user has the
    advantage of minimizing the file space needed for each user by not
    saving unwanted or unnecessary files. Saving all files unless specifically
    deleted is more secure for the user in that it is not possible to lose files
    inadvertently by forgetting to save them.

    Q:(midterm--2006--)
    Why do some systems keep track of the type of a file, while others leave
    it to the user or simply do not implement multiple file types? Which
    system is “better?”
    Answer:

    Some systems allow different file operations based on the
    type of the file Other systems leave such interpretation of a file’s data to the process
    and provide no help in accessing the data.

    The method that is “better” depends on the needs
    of the processes on the system, and the demands the users place on the
    operating system.

    For general-purpose systems it may be better to only implement basic file types to
    keep the operating system size smaller and allow maximum freedom
    to the processes on the system.


    Q:(midterm--2006--) what does OPEN and CLOSE do
    Answer:
    The open() operation informs the system that the named file is
    about to become active.
    The close() operation informs the system that the named file is
    no longer in active use by the user who issued the close operation.


    Q:(midterm--2006--) What is the sequential file access
    Answer:
    sequential file access:Information in the file is processed in order, one record after the other example(Print the content of the file)




    عدل سابقا من قبل Abd El-Hamid IbrahiM في الجمعة 5 يونيو 2009 - 1:21 عدل 1 مرات (السبب : add answer)




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    مُساهمة من طرف sandy.h في الأحد 17 مايو 2009 - 12:08

    Q:1 , exam 2006
    answer : slide 9 in ch 13

    Q:2, exam 2006
    answer : slide 12 in ch 13
    +
    DMA increases system concurrency by allowing the CPU
    to perform tasks while the DMA system transfers data via the system
    and memory buses. Hardware design is complicated because the DMA
    controller must be integrated into the system, and the system must
    allow the DMA controller to be a bus master. Cycle stealing may also
    be necessary to allow the CPU and DMA controller to share use of the
    memory bus.


    Q.3.2006 Define (Location transparency,Location independence)
    answer :
    1. Location transparency. The name of a file does not reveal any hint of the
    file's physical storage location.

    2. Location independence. The name of a file does not need to be changed
    when the file's physical storage location changes.


    Q.4.2006 (A Comparison of Caching and Remote Service)
    answer :
    slides 14,15 in chapter 7

    Q:5 ,exam 2006) What are the main differences between capability lists and access lists?
    answer: An access list is a list for each object consisting of the domains
    with a nonempty set of access rights for that object. A capability list is
    a list of objects and the operations allowed on those objects for each
    domain.


    Q:6 , exam 2006 ) What protection problems may arise if a shared stack is used for parameter
    passing?
    answer: The contents of the stack could be compromised by other
    process(es) sharing the stack.


    Q:7, exam 2006)
    cancelled question

    Q:8, exam 2006)
    answer: i think slide 8 in chapter 15 is the answer of this Q


    Q:9,10,11 exam 2006)
    cancelled question
    ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ

    novaber 2008
    ــــــــــــــــــــــــــــــــــــَ

    Q1:
    answer : slide 9 in ch 13

    Q3:What problems could occur if a system allowed a file system to be
    mounted simultaneously at more than one location?
    answer: There would be multiple paths to the same file, which could
    confuse users or encourage mistakes (deleting a file with one path
    deletes the file in all the other paths).


    Q4:
    answer : slide 21 + 24 in ch 13

    Q5:
    answer : 1- The host repeatedly reads the busy bit until that bit becomes clear.
    2-the host sets the write , bit in the command register and writes abyte into the data-out register
    3- the host sets the commend-ready bit .
    4- when the controller notics that the command-ready bit is set , it sets the busy bit .
    5- the controller reads the command register and see the write command
    it reads the data out the register to get the byte and does the I/O device.
    6- The controller clears the command-ready bit , clears the error bit in the stauts register to
    indicate that the device I/O succeeded , and clears the busy bit to indicat that it is finished .


    Q7:Capability lists are usually kept within the address space of the user.
    How does the system ensure that the user cannot modify the contents
    of the list?
    answer: A capability list is considered a “protected object” and is
    accessed only indirectly by the user. The operating system ensures the
    user cannot access the capability list directly



    Q8:when a program written by one user may be used by another user , an unexpected behavior may ensure describe briefy common methods by which such behavior accurs ?

    answer:If these programs are executed in a domain that
    provides the access rights of the executing user, the other users may misuse
    these rights


    ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ
    january 2007
    ============

    Q2:List four ways a system could use to determine which sectors are free.
    Give advantages of each way.
    answer:
    a.
    Free-space list. Each section indicates a sector that is available. Not encumbered by a used-sector list.
    b.
    Bit vector is a compact version. Has no links that can be broken.
    c.
    Link all free sectors together in an available list. Takes no usable space. But links could break.
    d.
    List giving start of each block of free sectors, and a count of number of sectors in this block. This is fast for use in contiguous storage search.



    عدل سابقا من قبل Abd El-Hamid IbrahiM في الأحد 7 يونيو 2009 - 0:15 عدل 4 مرات (السبب : add answer)




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    KatKat
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    مُساهمة من طرف KatKat في الخميس 4 يونيو 2009 - 15:43

    شكرا شكرا شكرا يا فتاه Very Happy

    Abd El-Hamid IbrahiM
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    مُساهمة من طرف Abd El-Hamid IbrahiM في الخميس 4 يونيو 2009 - 16:47

    الف شكر يا بشمهندسه





    Abd El-Hamid IbrahiM
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    مُساهمة من طرف Abd El-Hamid IbrahiM في الجمعة 5 يونيو 2009 - 1:24

    added the solution of the missed questions in the exames (january2006,mid2006,midterm2006) files





    Abd El-Hamid IbrahiM
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    مُساهمة من طرف Abd El-Hamid IbrahiM في الجمعة 5 يونيو 2009 - 12:53

    ملحوظة : يا جماعه السؤال بتاع ال worm
    انا كنت حضرت متاخر ف المحاضره ديه وهو الدكتر بيااخد الغيااب
    فا حد يدخل يقول اذا كان الworm معانا ولا لا
    لو معانا يبقى السؤال الى علي الworm ف الامتحانات بتاعت 2006 الى انا كتبت تحتيه cancelled ده معانا





    esis mohammed
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    مُساهمة من طرف esis mohammed في الجمعة 5 يونيو 2009 - 14:10

    ايوة يا فندم الدكتور وقف لحد ال Port Scanning يعنى اخدنا ال worm
    والسؤال كمان معانا
    ربنا يستر Sad

    ahmed sultan
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    مُساهمة من طرف ahmed sultan في الجمعة 5 يونيو 2009 - 14:16

    فعلا وصلنا للـ Worms
    واللى كان يهم الدكتور هنا انها بتتنقل للاجهزه عن طريق الشبكه وبس










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    مُساهمة من طرف Abd El-Hamid IbrahiM في الجمعة 5 يونيو 2009 - 14:41

    شكرا Sad





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    مُساهمة من طرف 3ABED في الجمعة 5 يونيو 2009 - 14:59

    اسمحلى اعدل على اجابتك يا عبد الحميد شويه
    -bit list or bit vector:the free space is implemented as a bit map in which each block is represented by 1 if it's free 0 other wise
    simplicity and efficiency in finding the first free block
    -liked list :we link together all free blocks with a pointer to the first block stored on a special place on the disk and cache it in the memory
    The FAT method incorporates
    free-block accounting into the allocation data structure. No separate method is
    needed.

    grouping : storing the addresses of n-free blocks in the first free block
    faster than the standard linked list
    counting:rather than keeping alist of free blocks we keeps the address of the first free block and n number of the free contiguous blocks that follow that block
    the overall list would be shorter
    عبد الحميد ممكن تشيل الاستفسارات اللى فى النص عشان الموضوع يبقى اجابات واسئله بس

    3ABED
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    مُساهمة من طرف 3ABED في الجمعة 5 يونيو 2009 - 20:11

    Q4: nov 2008
    i think 25 and 26 also

    sandy.h
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    مُساهمة من طرف sandy.h في السبت 6 يونيو 2009 - 12:56

    exam 2009
    ـــــــــــــــــــــــــــــــ

    Q1:-What is the meaning of the term busy waiting ? What other kinds of
    waiting are there in an operating system> can busy waiting be
    avoided altogether? Explain your answer

    Busy waiting meansa process is waiting for a condition to be satisfied in a tight loop without relinquishing the processor

    Alternatively, a process could wait by relinquishing the processor,
    and block on a condition (e.g., I/O, semaphore) and wait to be awakened at some appropriate time in the future.

    Busy waiting can be avoided butincurs the overheadassociated with:
    putting a process to sleepand having to wake it upwhen the appropriate program state is reached.


    Q2:- 11.5 in sheet
    Q3:- 13.1 in sheet
    Q4:- 13.5 in sheet
    Q5:- 14.9 in sheet
    Q7:- 11.7 in sheet

    Q8:-What is the difference between computation migration and process migration? Which is easier to
    implement, and why?

    Process migration is an extreme form of computation migration. In computation migration, an RPC
    might be sent to a remote processor in order to execute a computation that could be more efficiently
    executed on the remote node. In process migration, the entire process is transported to the remote node,
    where the process continues its execution. Since process migration is an extension of computation
    migration, more issues need to be considered for implementing process migration. In particular, it is
    always challenging to migrate all of the necessary state to execute the process, and it is sometimes
    difficult to transport state regarding open files and open devices. Such a high degree of transparency
    and completeness is not required for computation migration, where it is clear to the programmer that
    only a certain section of the code is to be executed remotely. programmer

    Q9:- 17.1 in sheet

    ----------------------------
    thnx to eng . abdelhamid for exam




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    مُساهمة من طرف Abd El-Hamid IbrahiM في السبت 6 يونيو 2009 - 22:35

    answers of nov2007 exam
    -------------------------------------

    Q1:13.2 in sheet

    Q2:15.1 in sheet

    Q3:11.2 in sheet

    Q4:Kernel I/O Subsystem?
    Scheduling
    Some I/O request ordering via per-device queue
    Buffering
    store data in memory while transferring between devices
    Caching
    fast memory holding copy of data
    Spooling
    hold output for a device,If device can serve only one request at a time
    Device reservation
    provides exclusive access to a device,System calls for allocation and deallocation,Watch out for deadlock

    Q5: Definetions..

    1)PCB(process control block)-->contains informations associated with each process as (process state,program counter,cpu registers,cpu scheduling info, accounting info and I/O status info)

    2)System calls --> provide interface in which passing parameters between a running programs and the operating system

    3)FCB(file control block)--> contains informations about the file including (owenership,permissions and location of the file contents)

    4)Boot Control block --> contains informations needed by the system to boot an operating system from specefic volume

    5)capability list --> is a list of objects and operations allowed on thoes objects for each domain

    6)access list --> is a list for each object consisting of domains with a none empty set of access rights for that object

    Q6:canceled Q
    Q7:14.6 in the sheet and i think 14.5 is important too






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    مُساهمة من طرف my fate في الأحد 7 يونيو 2009 - 0:31

    جزاكم الله خيراااااا
    cheers cheers

      الوقت/التاريخ الآن هو السبت 1 نوفمبر 2014 - 13:26