Page 19 - DCAP105_WORKSHOP_ON_COMPUTER_HARDWARE_AND_NETWORK

Unit 1: Introduction to Hardware and Software

Data is stored inside a computer in the memory. The storage capacity of a memory device is Notes
measured in the following units:
1 Nibble = 4 bits

1 Byte = 8 bits
1 Kilobyte (KB) = 1024 Bytes (210)
1 Megabyte (MB) = 1024 KB
1 Gigabyte (GB) = 1024 MB

1 Terabyte (TB) = 1024 GB
These devices are non-volatile. The stored data remains there as long as not erased intentionally.

Magnetic Storage Devices

This type of storage device has a layer of coating of some magnetic substance on a rigid or
flexible surface. The drive is equipped with a read-write head assembly that can convert the data
and instructions represented in the form of 0 and 1 into some form of magnetic signal. These
magnetic signals can then be stored on the medium.

 Floppy disks: Floppy disk was introduced by IBM. The first floppy disks used to be 8-inch
in diameter. As it got smaller and smaller gradually it started being called diskette. Next
smaller diskette was 5.25-inch in diameter. These days’ 3.5-inch diameter diskettes having
1.44 MB storage space are most popular on microcomputers for storing data and programs.
You can easily calculate that as many as 400 pages of printed book can be stored on a single
floppy disk.
A floppy disk is provided with a small sliding switch called write-protect notch.

!
Caution If this switch is on (that is when you can see through the whole from one side to
another) nothing can be written on the disk. This facilitates data safety. If this switch is on,
your data cannot be deleted.

Figure 1.15: Floppy Disk

 Hard disks: Hard disks have existed since 1950s. Earlier they used to be 20 inches in
diameter, holding just a few megabytes. Hard disks have hard platters that hold the
magnetic medium, as opposed to the flexible plastic film found in tapes and floppies.
A hard disk is able to store a large amount of information in a small space (usually 40GB).

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