Introduction

In a computer there are 2 types of storage mediums available
a) Primary Storage.
b) Secondary Storage.

Primary Storage : This storage medium is volatile in nature. ie it stores data temporarily and
when the computer is switched off the data stored is disappeared. So one can't use this medium
to store the day to day life's data and also the size of such storage media is not big.
eg: RAM.

Secondary Storage: Hence the need for secondary storage developed. This storage media is non volatile in nature. ie the data once stored never erases unless erased manually. Since i have chosen to write a blog on Secondary Storage Devices. So will like to share more info on these devices.

Types of Secondary Storage Devices:
a) Floppy Disks
b)Hard Disks
c)Pen Drive
d) DVDs/CDs

CDs/DVDs

CDs/DVDs works on the optical disc storage technology. CD stands for the Compact Disc and DVD stands for Digital Versatile Disc. A DVD/CD is composed of several layers of plastics and each layer is created by injection molding polycarbonate plastic.Data is encoded in the form of small pits and bumps in the track of disc.The encoding is done by a sharp laser beam.While reading the laser beam detects the pits and bumps and the combination of these gives a stream of bits which can be interpreted as characters by the computer.

Physical Formats:
DVD-ROM,CD-ROM
DVD-R, CD-R
DVD-RAM or DVD+RW, CD+RW

Logical Formats:
DVD-Video
DVD-Audio
Audio CD
Video CD
MP3 CD
Super Video CD

Pendrives

Pen drive is a small removable Flash Memory drive which is connected to the usb port.It is an plug and play device.Plug and Play device means it does not require any external power supply or software to run on a computer.It takes power from the usb port itself and when connected to the usb port, the OS automatically recognizes it. now a dys the storage capacity of pen drive has increased.They are available in the range from 1gb-80gb. Pen drives is a memory chip,the computer reads/writes to the pen drive as it would do to the ram.




Advantages :
a) Portable and compact
b) Massive storage capacity.
c)It is an solid state drive(No moving internal parts)
hence less chance of damage and corruption.

Hard Disk Drives

Hard disk drives are non volatile devices.A hard disk is a device which is permanently fixed in to the computer.IBM had developed the idea of the Hard Disk.An hard disk consists of following things, a platter, read n write head,spindle motor etc. An hard disk records the data on the platter which looks like the CD but unlike CDs it uses magnetism to store the data.The platter rotates at a very high Speed of 7200rpm with the help of Spindle motor and the read/write head writes or read the data in the form of 0's and 1's from the platter. The video below explains the concept.






Advantages:
a) Hard disk provides information at a very fast rate compared to the floppy disks
b) Since now a days portable external hard disks are available, so it has becomes easy to store a backup of large size of data.


Disadvantages:
a) Though Hard disks are reliable enough sometimes they can even crash due to mechanical failure or crash.
b) Hard disks are bulky enough compared to other devices such as pendrives etc.

Floppy Disks

Floppy Disks were introduced in the year 1971,these disk were 8 inch in diameter having a approx capacity of 1 mb. It contain the plastic disc with magnetic coating enclosed in cardboard case.The disks had read and write heads through which the data was accessible. Later in 1976,5.25" disks were introduced which were Because of such small size of storage, one had to maintain so many floppies to store a data which was in large size.Also these disks were very sensitive,one had to take lot of care to maintain it because they used to get corrupted very fast due to environmental factors such as dust, rise in temperature etc. Hence people started diverting towards the other storage medias such as CD or hardisks.

















Advantages:
a) Floppies were portable in nature,so one could easily transfer the data from on computer to the other.
b) Data was accessible at a very fast rate.
c) They were not expensive.

Disadvantages :
a) Floppy disks have less storage capacity and the transfer rate as compared to its counterparts suchs as CDs and pendrives etc.
b) It tends to get corrupted very fast due to physical conditions such as moisture,dirt etc.