Page 16 - Viva ICSE Computer Studies 4 : E-book

As it is clear from the name, ROM is read type of memory which can be read only and
not written by the user/programmer. It contains a number of programs. The Basic Input/
Output System (BIOS) is the most important program of ROM. This program activates
the hardware to communicate with the system and the application software.

External Memory

External memory stores information for a longer period of time. It is also called secondary
memory. Data and information stay protected in the secondary memory even if the
computer is switched off . Secondary memory is required because primary memory of a

computer has limited storage. Accessing data from secondary memory takes more time
than accessing it from primary memory.

Storage Devices

Storage devices are used by a computer to store data and information. Let’s learn about

diff erent storage devices.

Hard Disk Learn More

Hard Disk or Hard Disk Drive (HDD) is the
A hard disk is also known as ‘Winchester
most common magnetic, mass-storage
Disk’ because this device was fi rst made
device of present-day microcomputers, by IBM at Hursley Laboratory located near
which is fixed inside a computer and is not Winchester in England.
easily removable.

A hard disk is made up of disk platters, which are used to read and write on the disk.
These platters are sealed inside a box. There are diff erent types of hard disks available in
the market with diff erent storage capacities such as 80 GB, 160 GB, 250 GB, 300 GB and

500 GB.

Compact Disk (CD)

Compact Disk (CD) is an optical storage media. It is round in shape and is a shiny disk.
Earlier CDs were of read-only type but now writable CDs are available with the relevant
drives (such as CD Writer) to write on them. A single optical disk stores nearly 640 MB of

data. A large multimedia software and data such as audio/video fi les can be stored on
the CDs.

Digital Versatile Disk (DVD)

Digital Versatile Disk (DVD) is an optical disk with capacity varying from 4.7 GB to 17 GB.

DVDs are the higher capacity removable media for multimedia applications.

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