Tuesday, April 17, 2012
SECONDARY MEMORY: The magnetic memory is used as secondary and backup memory.
It is employed for bulk storage of programs, data and other information. It has
much larger capacity than main memory. It stores system software, assemblers,
compilers, useful packages, large data files etc. the secondary memory should
not be of volatile nature. It must store information permanently. The magnetic
memories such as hard disks are the most common secondary memories used in
computers.
HARD DISK
§ Hard disks are o n-line storage device. The term on-line means that the
device is permanently connected to the computer system.
§ Hard disk is made of aluminum (or other metal or metal
alloy) with a thin coating of magnetic material (iron oxide) over it.
§ Standard size
of hard disk is 3.5 inch. The 2.5 inch disks are used in portable computers.
Floppy
disks are made of Mylar (a plastic material) coated with magnetic material
(iron oxide or barium ferrite). The disk is not a hard plate, rather it is very
thin piece of flexible plastic, and hence, it is called Floppy disk. Floppy
disks are also called diskette. They are removal disks. The size of the floppy
disk is 3.5 inch diameter. A floppy disk rotates at 360 rpm. Its average access
time is 150-250 ms.
OPTICAL DISKS
Optical
disks are used for backup memory. Information is written to or read from an
optical disk using laser beam. It has very high storing capacity as compared to
magnetic floppy disks. An optical disk is a direct access device. It can be randomly
accessed for music, video, a file or any other information.
There
are following types of optical disks:
(i) CD (Compact disk) or CD-ROM
(ii) CD-RAM (CD Recordable)
(iii) CD-RW (CD-Read/Write)
(iv) DVD (Digital Versatile Disk)-ROM
(v) DVD-R
(vi) DVD-RW
Every weekend i wont to head to see this electronic computer, as a result of i want for enjoyment, for the explanation that this this electronic computer conations dedicated funny info too.
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