Page 20 - DCAP105_WORKSHOP_ON_COMPUTER_HARDWARE_AND_NETWORK

Workshop on Computer Hardware and Network

Notes A hard disk can also access any of its information in a fraction of a second. Unlike floppy
disks hard disks are packed with the drive itself. A typical hard-disk drive looks like the
one shown below.
Figure 1.16: Hard Disk

Hard disks have very large capacity. They are thus used to store data and programs that
are very frequently used. Because of their fast speed they mostly act as active storage or
online storage rather than backup storage.

Hard disk drives are fixed inside the computer casing and hence are not easily removable.
They are not as portable as floppy disks are. However, some hard disks are detachable and
can be inserted into a drive just like floppy disks.
Hard disks are very delicate and can easily get damaged if some pressure is applied on the
drive. It can also get damaged if it suffers jerks when it is being carried from one place to
another. It is also very sensitive to power fluctuations.
 Magnetic tapes: Magnetic tapes are similar to the tapes that you see in audio cassettes or
video cassettes. Large computer systems use this medium for data storage purposes mostly
as data backup. They are strictly sequential access media. Tapes are divided into tracks
(usually 7 or 9 in number) running parallel to the length of the tape. One of the tracks is
used to detect data transmission errors and to control them. Magnetic tapes can store as
much as 10GB of data. It is reusable. You can erase it and rewrite new data. It has high data
transfer rate and is yet cheap. However, the main disadvantage of a magnetic tape is that
it allows only sequential access. The records cannot be easily updated and modified without
copying them on another medium. Tapes are not long lasting and are very vulnerable to
heat and magnetic disturbances.

 Zip disks: Zip disks are similar in looks to floppy disks. They are slightly bigger and
thicker than floppy disks. On a Zip disk however, the magnetic coating is of much higher
quality. The read/write head is significantly smaller than that of a floppy disk (by a factor
of 10 or so). The smaller head, combined with a head positioning mechanism similar to
that used in a hard disk enables a Zip drive to pack thousands of tracks per inch on the
track surface. Zip drives also use a variable number of sectors per track to make the best
use of disk space. All of these things combine to create a floppy disk that holds a huge
amount of data.

Notes Their capacity typically lies between 100MB and 250MB, making them ideally
suited for backing up data and programs from the hard disks.

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