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Author: Atika M. Nyamoti
Secondary storage devices
These are devices that store data permanently. They are classified into two categories namely: Magnet and Optical disks.
Magnetic Disks
These are disks that use magnetic technology to save data examples include:
The Hard Disk/HDD
-A hard disk is part of a unit, often
called a "disk drive,"
"hard drive," or "hard disk drive," that store and
provides relatively quick access to large amounts of data on an
electromagnetically charged surface or set of surfaces. A hard disk is really a set of stacked
"disks," each of which, like phonograph/ gramophone records, has data recorded
electromagnetically in concentric circles or "tracks" on the disk. A
"head" (something like a phonograph arm but in a relatively fixed
position) records (writes) or reads the information on the tracks. Two heads,
one on each side of a disk, read or write the data as the disk spins. Each read
or write operation requires that data be located, which is an operation called
a "seek." (Data already in a disk cache, however, will be
located more quickly.)
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| Parts of the Hard Disk |
Disk platter
A hard-disk platter (or disk) is a component of a hard-disk
drive: it is the circular disk on which the magnetic
data is stored. The rigid nature of the platters in a hard drive is what gives
them their name (as opposed to the flexible materials which are used to make floppy disk). Hard drives typically have several platters which are
mounted on the same spindle. A platter can store information on both sides, requiring
two heads per platter.
Other magnetic disks
include: Zip disks, Jazz disks and magnetic tapes
Off-line/removable
storage devices
Magnetic disks
Floppy disk- The term usually refers to the magnetic
medium housed in a rigid plastic cartridge measuring 3.5 inches square and
about 2millimeters thick. Also called a "3.5-inch diskette," it can
store up to 1.44 megabytes (MB) of data. Although many personal computers today
come with a 3.5-inch diskette drive pr-installed, some notebooks and centrally-administered desktop
computers omit them. Floppy disk requires floppy
drives (shown below) to read and write.
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| floppy drive(used to read floppy disks |
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| Parts of a floppy Disk |
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| Floppy Disk |
Other magnetic discs include:
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| Zip Disks with a capacity of 250MB |
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| Jazz Disk |
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| Magnetic Tape (80MB-5TB) |
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| Magnetic Stripe (1607 bits approx: 1.4 bytes) used by credit card |
Next: Optical Disks
These are devices that store data permanently. They are classified into two categories namely: Magnet and Optical disks.
