Secondary memory comprises peripheral devices that are slower but much cheaper than internal memory. These devices do not lose stored information even after the power is switched off. Hard disks, floppy disks, compact disks, magnetic tape, video disks, magneto-optical drives, DVDs, etc are used as secondary Memory.
HARD Disk
It is fixed inside the computer and is not easily removable, also called fix this drive .
It is used for storing the software and the data inside computer.it is known as Winchester Disk because this drive was first made by IBM at Horsley laboratory located Winchester in England. this disk consists one or more disk platters and access mechanism and read/ write head which are seen in a case.
Hard Disk size depends upon their this platters diameter". different sized platters are 51/2 ,31/2 , 21/2 inch .31/2 inch size platter is common with PC and 21/2 inch with laptop portable computer read write head is used to write any information on the disk surface or to read it back.
Storage capacity of hard disc from 10 MB to 6.3 GB but 4.3 GB are common part of Pentium computers.
Hard Disk
Floppy disk
FD is common storage device which is small flexible and easily removable .
It is made of plastic coated with magnetic material which is sealed inside a square plastic jacket .
It is called floppy because it is soft having flexible physical property.
Data can be written on or read from this floppy by a drive called floppy disk drive which is fixed inside the computer.
Types of floppy depend upon their size and storage capacity floppy drive that pack two high density floppy drive 5.25 and 3.5 inch into a single package is known as Combo Drive.
Types of Floppy Disk
Compact Disk
CD is a storage device used to store data information and software which can be read only and not to be changed or erased.
It is an optical read-only memory made of resin.it is called Compact Disk Read Only Memory.
The information is stored on CD by using an expensive dry called CD ROM drive is a very popular storage device for micro computers because a large number of software including multimedia audio and graphic software are available only on this disk.
Compact Disk can store a large volume of data up to 680 MB which is almost the same as the storage capacity of a 630 MB hard disk.
WORM -Write Once Read Many It is a type of Compact Disk which can be recorded only once and not erased. it can store more data than CD ROM generally measured in gigabytes.
Magnetic Tape
It is the oldest storage device available for microcomputer, it is generally used to store large volume of data that is needed to be sequentially accessed and processed.
The tape is made of a plastic ribbon coated with an iron oxide material which can be magnetized the data store on the tab can be read as well as raise and return again
Magnetic Tape is a sequential access storage device as it is possible to read the data randomly or directly.
It is suitable only for storing data for backup and batch mode applications and not for online application.
Video Disk
It is used to store text video and audio data it is widely used for training application as it can be played like a photograph record.
Magnetic Optical Drive
This is the latest of all storage device used both as laser and electromagnet to record data on a removable cartridge.
The surface of cartridge contain tiny embedded magnets.The unique feature of MO drive is that it has a very high storage capacity.
MO drive is costlier and slower than HDD. It has a long life and is more reliable.
DVD RAM
DVD RAM uses very different technology from CD and DVD. they have the following features
Instead of a single spiral track, they use in a number of concentric track
Use of a concentric track allows simultaneous read and write operations to take place.
They allowed numerous read and write operations up to 100000 times and have great longevity over 30 years which makes them ideal for achieving.
Blu Ray Disk
It is a optical media storage device dimension as standard cd- roms or DVD is single layer Blu ray disk can hold about 25 GB of data.
Blu-Ray Disk
Difference among Disk
USB Flash Memory
They connect to computer through the USB port. The main advantage is that they are very small lightweight device which make them suitable as a method for transferring file between computer and also be used as small backup device for music or photo files.
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