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لان كل نظام له تطبقات

الفوارق من ناحيه الفوائد والمساوئ

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• Advantages of dbms
It means all of the information is together.
The information is easy to access at any time.
It's more easily retrievable.
Many people can access the same database at the same time.
Improved data security.
Reduced data entry, storage, and retrieval costs.

DISADVANTAGES…
Database systems are complex, difficult, and time-consuming to design.
Initial training required for all programmers and users.
Suitable hardware and software start-up costs.
A longer running time for individual applications.
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Advantages and disadvantages of relational DBMS :

the most flexible of the database models

no obvious match of implementation to model - model is the user's view,
not the way the data is organized internally

is the basis of an area of formal mathematical theory

most RDBMS data manipulation languages require the user to know the contents of relations,
but allow access from one relation to another through common attributes
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Advantages of Object relational DBMS :
The main advantages of extending the relational data model come from reuse and sharing.
Reuse comes from the ability to extend
the DBMS server to perform standard functionality centrally,
rather than have it coded in each application.
If we can embed the functionality in the server,
it saves having to define it in each application that needs it, and consequently allows the functionality to be shared by all applications
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Advantages and disadvantages of Distributed DBMS

The information system manager must make decisions on whether to use centralized or de-centralized databases based on a number of issues including the following:

* Decentralized databases exchange files and therefore may exchange corrupted files or viruses that may affect the entire system. Security of these databases are difficult to maintain. Though the section on Data-less information systems discusses how these systems can be used to create more confidential information exchanges.
* In decentralized databases the type of data to be exchanged, the process of addressing the data, and the protocol for updating the data must be agreed upon ahead of time and plans must be in place for updating the process.
* In centralized databases lack of backup or inadequate back up may result to complete loss of data while in distributed data systems data loss is limited to nodes affected.
* De-centralized databases are more flexible and allow different units to update and maintain their own data. At the same time, this increased flexibility runs the risk that some units may institute changes that may make them less accessible by others.
* When different groups and systems are involved in maintaining the data, then there is more opportunity for differences in quality of data to emerge. A decentralized database needs to have procedures for determining the quality (accuracy, recency, reliability, etc.) of the data.d

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مشكووور الله يعطييييييييييييييييييك الف عااافيه
ماقصرت

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تحت خدمة الجميع الله يبارك فيك

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السلام عليكم

مطلوب مني بحث بحدود صفحه واحده فقط وتسليمه غدا
"Fram Switching"
وشكرا

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المشاركة الأصلية كتبت بواسطة أعشق خطآه   السلام عليكم مطلوب مني بحث بحدود صفحه واحده فقط وتسليمه غدا "Fram Switching" وشكرا

هل تقصدين :
frame switching ?

Using frame switches to speed up network traffic.
For example, when a 10Base-T Ethernet hub is replaced with an Ethernet frame switch, each sending and receiving pair of stations obtains the full bandwidth of the network . A network device that switches variable-length packets from sender to receiver. Ethernet, Token Ring and FDDI switches are examples. .Using cell switches to forward fixed-length packets in a network.(Asynchronous Transfer Mode) A network technology for both local and wide area networks (LANs and WANs) that supports real-time voice and video as well as data. The topology uses switches that establish a logical circuit from end to end, which guarantees quality of service (QoS). However, unlike telephone switches that dedicate end-to-end circuits, unused bandwidth in ATM's logical circuits can be appropriated when needed. For example, idle bandwidth in a videoconference circuit can be used to transfer data.ATM is widely used as a backbone technology in carrier networks and large enterprises, but never became popular as a local network (LAN) topology . ATM is highly scalable and supports transmission speeds of 1.5, 25, 100, 155, 622, 2488 and 9953 Mbps. ATM is also running as slow as 9.6 Kbps between ships at sea. An ATM switch can be added into the middle of a switch fabric to enhance total capacity, and the new switch is automatically updated using ATM's PNNI routing protocol.

Cell Switching
ATM works by transmitting all traffic as fixed-length, 53-byte cells. This fixed unit allows very fast switches to be built, because it is much faster to process a known packet size than to figure out the start and end of variable length packets. The small ATM packet also ensures that voice and video can be inserted into the stream often enough for real-time transmission.

ATM works at layer 2 of the OSI model and typically uses SONET (OC-3, OC-12, etc.) for framing and error correction out over the wire. ATM switches convert cells to SONET frames and frames to cells at the port interface.

Quality of Service (QoS)
The ability to specify a quality of service is one of ATM's most important features, allowing voice and video to be transmitted smoothly

حطي اللي تبين وشيلي اللي ماتبين
حطي الماوس و شوفي
cell switch
cell switching
desktop switch
frame switch
LAN switch

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ايه أخطأت بكتابتهااا

مشكور وجــــــــــــــــــــــــــــــــــــــــــــــــ ــــزااااك الله ااااالف خير اخوي فيصل

[عبدالله الفـارس]

جزيت خيراً استاذ فيصل على مجهودك الطيب

أشكرك

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يسعد مسآك اخوي فيصل
ممكن حل الاسئلهـ لاهنت...

1- Define and write the different between SRAM , DRAM

2-write the devices that control by BIOS in your PC

3-write the value of data that control by cmos

4- write T or F
a- we can use 2Ram in computer ()
b- we can use 2Ram in process in computer()
c-BIOS on of Ram memory type()

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Static RAM is more expensive, requires four times the amount of space for a given amount of data than dynamic RAM, but, unlike dynamic RAM, does not need to be power-refreshed and is therefore faster to access. One source gives a typical access time as 25 nanoseconds in contrast to a typical access time of 60 nanoseconds for dynamic RAM. (More recent advances in dynamic RAM have improved access time.) Static RAM is used mainly for the level-1 and level-2 caches that the microprocessor looks in first before looking in dynamic RAM.
Dynamic RAM uses a kind of capacitor that needs frequent power refreshing to retain its charge. Because reading a DRAM discharges its contents, a power refresh is required after each read. Apart from reading, just to maintain the charge that holds its content in place, DRAM must be refreshed about every 15 microseconds. DRAM is the least expensive kind of RAM.
The initial function of the BIOS is to identify, test, and initialize system devices such as the video display card, hard disk, floppy disk and other hardware. The BIOS sets the machine hardware into a known state, so that software stored on compatible media can be loaded, executed, and given control of the PC.

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مشكوور اخوي بس بسألكـ هذي إجابهـ السؤال الاول صح

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المشاركة الأصلية كتبت بواسطة فيصل المرشد   السؤال الاول : Static RAM is more expensive, requires four times the amount of space for a given amount of data than dynamic RAM, but, unlike dynamic RAM, does not need to be power-refreshed and is therefore faster to access. One source gives a typical access time as 25 nanoseconds in contrast to a typical access time of 60 nanoseconds for dynamic RAM. (More recent advances in dynamic RAM have improved access time.) Static RAM is used mainly for the level-1 and level-2 caches that the microprocessor looks in first before looking in dynamic RAM. Dynamic RAM uses a kind of capacitor that needs frequent power refreshing to retain its charge. Because reading a DRAM discharges its contents, a power refresh is required after each read. Apart from reading, just to maintain the charge that holds its content in place, DRAM must be refreshed about every 15 microseconds. DRAM is the least expensive kind of RAM. السؤال الثاني : The initial function of the BIOS is to identify, test, and initialize system devices such as the video display card, hard disk, floppy disk and other hardware. The BIOS sets the machine hardware into a known state, so that software stored on compatible media can be loaded, executed, and given control of the PC.

شكراً

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3

cmos is only amedium for storge
in pc's there is small amount of memory in a speical cmos RAM chip
the data is maintained with electric power from a small battery>
it could be used for any type of data

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4- write T or F
a- we can use 2Ram in computer ( T)
b- we can use 2Ram in process in computer(T)
c-BIOS on of Ram memory type(T)d

[فهد المنيع]

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