Page 69 - Computer - 9(A&B)

ROM (Read Only Memory)

It stores the start-up instructions for the computer. It holds these instructions even after
the power supply is switched OFF. Hence, it is a permanent memory. These instructions
cannot be overwritten, but can only be read.

A computer with more capacity of RAM works faster
than a computer with lesser capacity of RAM.

Secondary Memory Devices

Secondary memory is needed in the computer to store information for a long period of time. It is also called
external memory. The secondary memory is permanent which holds the data even after the computer is shut
down. Examples of secondary storage devices are CD, DVD, Blu-ray disc, pen drive, memory card, hard disk,
etc.

Hard Disk
It is the main secondary storage device that stores large amount of data permanently,
which can range from 500 GB to 5 TB. It is present inside the CPU box. A hard disk stores
operating system software, application software and all other fi les and folders saved in a
computer.

External Hard Disk: This hard disk is connected externally to a
computer through a USB port, just like a pen drive. It can store
large amount of data just like an internal hard disk, and it can be
carried along
External Hard Disk USB Port
CD (Compact Disc)
It is a portable storage device that stores data permanently. Its storage capacity is up to 700 MB. There are many
types of CDs. Rapid Fireapid Fire
R
 CD-ROM (CD-Read Only Memory) Which memory is volatile
in nature?
 CD-R (CD-Recordable)

 CD-RW (CD-Read Write)
DVD (Digital Versatile Disc)
It is also a portable storage device. It is similar to CD, but it has more capacity to
store data. Its storage capacity can be up to 17.08 GB. CD and DVD

Knowledge Plus
Knowledge Plus
A CD drive can read data from a CD. A DVD drive can read data from both a CD as well as a DVD.

Blu-ray Disc
It is a scratch resistant disc that can safely store data for a long time. It uses blue-violet laser
light technology. Its storage capacity can range from 25 GB to 50 GB.

Pen Drive
It is a portable storage device that can be carried in a pocket. It is also called Flash drive or
USB drive. We can use a pen drive to transfer data from one computer to another computer. Its
storage capacity can be up to 1 TB.

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