Page 11 - Computer Genius Class 05
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Secondary Memory
This memory is permanent in nature and is not directly accessed by the CPU. It allows users
to store data that may be easily retrieved. It is cheaper compared to primary memory.
Secondary memory devices are also called secondary storage devices. They are categorised
into three types:
Secondary Storage Devices
Magnetic D isk O ptical D isc Flash D rive
H ard D isk CD D V D B lu- Ray D isc Pen D rive Memory Card
Magnetic Disk
A circular metallic disk covered with a magnetic coating, that is used for storing data, is
callled a Magnetic disk. You can record and erase data on a magnetic disk any number of
times.
Hard Disk
The hard disk consists of one or more magnetic disks called platters.
Each disk in the pack has top and bottom surfaces on which data
is recorded using a magnetic head. t is permanently fixed in the
computer system. It is usually used for permanent mass storage. The
most important function of the hard disk is to store program files
and data files.
The hard disk comes in a variety of sizes with storage capacities as
high as 5 TB (TeraByte) or even more. The CPU accesses data stored
on a hard disk much faster than it can access data on a CD.
External hard disks are also available. They are the hard disks that
can be connected to any computer with the help of a USB port.
The first hard dis as introduced y eagate in 1 hich could hold
5 MB of data.
Optical Disc
An optical disc is an electronic data storage medium that can be written to and read using
a low-powered laser beam. The lifespan of an optical disc is longer than a magnetic disk.
Data Storage and Memory 9

