Thursday, September 6, 2012
Monday, September 15, 2008
SEB070016-TUTORIAL5
TYPE OF DIRECT ACCESS STORAGE DEVICE
Magnetic Disk
DESCTIPTION
A memory device, such as a floppy disk or a hard disk, that is covered with a magnetic coating. Digital information is stored on magnetic disks in the form of microscopically small, magnetized needles, each of which encodes a single bit of information by being polarized in one direction (representing 1) or the other (representing 0).
Magnetic disc is the primary computer storage device. Like tape, it is magnetically recorded and can be re-recorded over and over. Disks are rotating platters with a mechanical arm that moves a read/write head between the outer and inner edges of the platter's surface. It can take as long as one second to find a location on a floppy disk to as little as a couple of milliseconds on a fast hard disk
EXAMPLE
HARD DISK AND FLOPPY DISK
ADVANTAGES
high storage capacity,
reliable gives,
direct access to data.
Optical Disk
DESCRIPTION
Is an electronic data storage medium from which data is read and written to by using a low-powered laser beam. It is flat, circular, plastic or glass disk on which data is stored in the form of light and dark pits. The laser beam reads the pits and the data can be accessed
EXAMPLE
Read-only optical disk,WORM,Rewritable/Magneto-optic disks
ADVANTAGES
An optical disk has much more storage capacity on the order of gigabytes, than a magnetic disk. It can hold up to 6GB of data in comparison to 1.44 MB of a diskette. Optical disks are inexpensive to manufacture. Data stored on optical disks is resistant to power surges or magnetic disturbances, such as head crashes or corruption form stray magnetic fields. Hence, they provide high data stability. Optical disks are less vulnerable to extremes of hot and cold as compared to the magnetic disks. Optical disks have long media life than magnetic disks.

Flash Memory
DESCRIPTION
Flash memory is non-volatile computer memory hat can be electrically erased and reprogrammed. It is a technology that is primarily used in memory cards and USB flash drives for general storage and transfer of data between computers and other digital products. It is a specific type of EEPROM (Electrically Erasable Programmable Read-Only Memory) that is erased and programmed in large blocks; in early flash the entire chip had to be erased at once. Flash memory costs far less than byte-programmable EEPROM and therefore has become the dominant technology wherever a significant amount of non-volatile, solid-state storage is needed.
EXAMPLE
thumb drive, key drive, and mini-USB drive.
ADVANTAGES
The advantages of flash memory as compared with HDDs are substantial. They include smaller size, lighter weight, a far lower power consumption, longer life expectancy and greatly improved shock resistance.


Magneto-optical Disk
DESCRIPTION
A magneto-optical drive is a kind of optical disc drive capable of writing and rewriting data upon a magneto-optical disc
EXAMPLE
magneto optical drive
ADVANTAGES
A magneto-optical disc comprising a recording layer and a protective coating on a substrate is operated for magneto-optical recording in a magnetic field modulation mode such that the protective coating is in sliding contact with a magnetic head.
Posted by muna at 11:13 PM 0 comments
Monday, September 1, 2008
SEB070016-TUTORIAL 4
LINUX | WINDOW |
how Linux implement virtual memory: The virtual memory feature of Linux makes the operating system behave as if it has a larger memory than the actual memory size. Linux moves blocks of memory called pages in and out of a special memory area, called swap space, in the hard disk. The MMU converts the address specified by the register, also known as the linear address, to the actual physical address for the data to be accessed. This process is termed page conversion and occurs in three stages of mapping: | How window perform and implements virtual memory: RAM generally not large enough to hold all of the running programs, so Windows sets up some additional virtual memory as a file on the hard drive. It then swaps portions of the programs between the physical and virtual memories, always having the currently active portion of a program in the physical memory. - Windows sets the default minimum size of virtual memory at 1.5 times that of the RAM, and the maximum size at 3 times the minimum. - Windows then manages the actual size, expanding and contracting it as needed within these limits.
|
uses demand paging to load executable images of the running program in the memory
| Doesn’t use demand paging. item that loaded in RAM is the non-paged area and page pool Page size: in Windows XP, when we added more memory to computer, we had to manually go and increase the size of your paging file to correctly match the amount of memory in your computer. Windows Vista does away with this by automatically setting the optimal size for the paging file, even after you add more memory to your computer. |
page fault handler determines what must be done to resolve this page fault 1) Find where the desired page resides on disk and read it in 2) Determine that the desired page is already in RAM and direct the MMU to point to it Kernel-handle page fault: identify the type of the requested virtual memory access and take the appropriate action to allow or deny application's VM request. | Using page handler 1) It can decide the virtual address is just simply not valid. In this case, Windows will report this error back by indicating an exception has occurred (typically STATUS_ACCESS_VIOLATION) -2) It can decide the virtual address is valid. In this case, Windows will find an available physical page, place the correct data in that page, update the virtual-to-physical page translation mechanism and then tell the hardware to retry the operation. When the hardware retries the operation it will find the page translation and continue operations as if nothing had actually happened. |
use signals, such as SIGSEGV , to report these error conditions to programs | uses structured exception handling to report page fault-based invalid accesses as access violation exceptions |
Thrashing issue could be reconcile with Resolving the excessive memory paging by temporarily helping one of the active processes quickly build up its working | Thrashing a process is busy swapping pages in and out -Increase the amount of RAM in the system to eliminate the cause of thrashing - Reduce the amount of RAM needed by reconfiguring the applications, removing unneeded system services (like network protocols that aren't being used), or running fewer applications at a time - Try to optimize the paging file's activity |
Posted by muna at 11:23 PM 0 comments
Thursday, August 28, 2008
ELE..TRICK
Orang Melayu dikatakan mengambil perkataan ELEKTRIK daripada perkataan Inggeris yang juga ELECTRIC. Tetapi yang sebenarnya, ELECTRIC itu diambil dari perkataan Melayu campur Inggeris.
Ceritanya… . Pada suatu masa dulu selepas setahun Thomas Edison mencipta lampu, saintis tidak pernah terfikir memberi nama kuasa yang menyebabkan lampu itu hidup. Jadi, entah macam mana semasa lampu mula-mula hendak diperkenalkan di Tanah Melayu, ada seorang Melayu yang bernama Kulup Kalimantang mati-mati tidak percaya pada hasil ciptaan Thomas Edison itu. Semasa demonstrasi diadakan oleh Thomas di Tanah Melayu untuk memperkenalkan lampu itu, Kulup Kalimantang pun berkata dengan kuat.
“Ele..trick aje tu… ele..trick aje… ele trick!”. ( Bermaksud tipu )
Thomas Edison berfikir Kulup berkata begitu kerana mengatakan lampu menyala disebabkan oleh kuasa “ele..trick” . Jadi digunakanlah perkataan “ELE..TRICK” yang dieja ELECTRIC mengikut ejaan orang putih. Sebagai mengingati jasa Kulup Kalimantang menamakan kuasa ELECTRIC itu, maka diciptalah sejenis lampu panjang yang dinamakan lampu kalimantang
Posted by muna at 12:47 AM 0 comments
Monday, August 25, 2008
computer-terminology-bm-vs-biharu-jadinya..
Some computer terms translated to BM,
Don’t you think that computer terminology in Bahasa Malaysia is really weird?
Cakera Keras = Hard Disk
Tetikus = Mouse
Papan Kunci = Keyboard
CD-ROM = Cakera Padat Ingatan Melalui Pembacaan (CP-IMP) - Isn’t that bit too much to ingat? Try pronouncing that without twisting your tongue or pausing to think. IMPs?
Monitor = What’s the term for this? KETUA DARJAH?
Modem = Could it be called “PEMPEND” <– PEModulasi, PENDemodulasi?
Motherboard = “Papan Ibu” probably? Maybe the best motherboards can be awarded the “Papan Ibu Mithali” then?
Sound Card = Kad Bunyi?
Sound Blaster = Peletup Bunyi?
Pipeline Burst Cache = Duite Garisan Paip Meletup?
Local Bus = Bas Tempatan? Sounds good to me.
VESA Local Bus = Bas Tempatan VESA?
Flatbed = Katil leper? OR Katil Rumah Pangsa (Flat)?
WWW = Sarang labah-labah Selebar Dunia (SSD)? Sounds quite convincing to me.
Then what would you call daughterboards? Papan anak perempuan? That sounds a little kinky for me :)) What about SIMMs and DIMMs and such…?
*laf* wonder what would you call ink jets then Pancutan Dakwat???
What about “Plug and Play [tm]“? Hmmm..Plug and play….Cucuk dan Main??? Somehow I think not.
Posted by muna at 11:16 PM 0 comments