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Explain Data Storage Devices in Detail

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Data Storage Devices

Data storage device is a device which is used to hold information temporarily or permanently in a structured way. By structured, we indicate that the information is an organization in a way that makes it is easy to retrieve after-the-fact.

These storage devices can be divided into two main categories:

  1. Magnetic Media which stores the binary data on a disk or tape coated with a material that can be magnetized differently, depending on whether 0 or 1 is stored.
  2. Optical Media which stores the binary data in a surface that reflects laser light differently, depending on whether a 0 or 1 is stored.

Magnetic Media

1. Floppy Disk:

An increasing popular direct access secondary storage medium for micro and minicomputer systems is the floppy disk. Floppy disks are also referred to as diskettes. A floppy disk is made of flexible plastic which is coated with magnetic oxide. The flexible disk is enclosed within a square plastic. Floppy disks are typically 3, 5.25 or 8 inches in diameter. They come in either single or double density versions and record on one or both surfaces of a diskette.

Advantages of Floppy Disk :

  • Floppy disks are very cheap as compared to other storage devices.
  • They greatly enhance the online storage capacity of small systems at an affordable price.
  • They are also a convenient offline storage medium for the small system.

2. Magnetic Disk:

A magnetic disk is a thin, circular metal plate coated on both sides with a magnetic material. It is very similar to LP gramophone record. A disk pack consists of a number of these disks, three or more, mounted about half an inch apart from each other on a central shaft which rotates at speeds of 2,400 or more revolutions per minute. Magnetic disks are the most popular medium for direct access secondary storage. In a disk pack, information is stored on both the surfaces of each disk plate except the upper surface of the top plate arid the lower surface of the bottom plate which is not used. Each disk consists of a number of invisible concentric circles called tracks. A set of corresponding tracks in all the surfaces is called a cylinder. Information is recorded on the tracks of a disk surface in the form of invisible tiny magnetic spots.

Advantages of Magnetic Disk :

  • The magnetic disk has the flexibility of being used as a sequential as well as a direct access storage device.
  • Magnetic disks are less vulnerable to damage from dust or careless handling.

3. Magnetic Tape:

Magnetic tape is one of the most popular storage medium for large data that are sequentially accessed and processed. Information is recorded on the tape in the form of tiny invisible magnetized and non-magnetized spots on the iron-oxide side of the tape. The tape is divided into vertical columns called frames and horizontal rows called tracks.

Advantages of Magnetic Tape :

  • The storage capacity of a magnetic tape is virtually unlimited because we can use as many tapes as required for recording our data.
  • A reel of tape is also a convenient way of carrying information from one place to another.

4. Winchester Disk :

In this unit, disks are permanently housed in sealed, contamination free containers. The disks are coated with a special lubricant which reduces friction when the read/ write heads land on the disk surface. The container is usually not removed from the disk drive. High capacity systems using these sealed housing are said to employ Winchester technology.

Advantages of Winchester Disk :

  • Winchester disks are fast and reliable.
  • Less expensive when compared with hard disk devices.
  • Winchester disks are used in all but the smallest computer systems.

Optical Media

1. Compact Disk Read Only Memory:

CD-ROM means compact disk – read only memory. It is the necessity to store a large volume of data that has led to the development of optical disk storage medium. Like a floppy disk, a CD-ROM only starts spinning when requested and it has to spin up to correct speed each time it is accessed. It is much faster to access than a floppy but it is currently slower than a hard disk.

Advantages CD-ROM :

  • Storage cost is very low.
  • CD-ROM’s hold large quantities of data.
  • Access time is relatively fast.

2. Write Once, Read Many (WORM):

The inconvenience that we can’t write any thing into a CD-ROM is avoided in WORM. A WORM allows the user to write data permanently on to the disk.

Advantages of WORM :

  • It can store vast amount of data.
  • Any document in a WORM can be accessed very fast.

Erasable Optical Disk:

These are optical disks where data can be written, erased and re­written. This also applies a laser-beam to write and rewrite the data. These disks may be used as alternatives to traditional disks.

Semiconductor Media :

Semiconductor Media Stores the binary data in semiconductors transistors.

For Example, Pen Drives, SD Cards etc.

Pen Drive:

A pen drive, or a USB flash drive is a portable data storage device. Pen drives have replaced the floppy drives of old and have become the most popular data storage devices among consumers.

Characteristics of Pen Drive :

  • These are very fast device for data transfer.
  • These are plug and play USB devices. It means, pen devices need not be installed.
  • Pen drive has high capacity of data storage. Its capacity range from 128 MB data to 8 GB and increasing day by data as the technology changes.
  • This is very portable and small in size with large capacity.
  • This is easy erasable and rewritable device. These are advantageous over CDs as these are rewritable and erasable.

SD Cards:

An SD (Secure Digital) card is an ultra small flash memory card designed to provide high capacity memory in small size. SD cards are used in small portable devices such as digital video camcorders, digital cameras, handheld computers, audio players.


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