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Storage Devices


Q.1. How can you classify Storage Devices? What are its different types elaborate?

Ans.: Storage devices or secondary storage devices are used to store data and instruction permanently. They are used in computers to supplement the limited storage capacity of RAM.

 Floppy Disk : It‟s a circular disk coated with magnetic oxide and enclosed within square plastic cover (Jacket). It‟s available in different size, but the most commonly used floppy is 3½. Data up to 1.44 MB can be stored in it. Data is written as tiny magnetic spots on the dish surface creating new data or a disk surface eraser data previously stored at that location. Floppies are available in 2 sizes, 3.5 inch & 5.25 inch. The 3.5 inch size floppy is mostly used. The 5.25 inch floppy is kept in a flexible cover & it‟s not safe. It can store about 1.2 MB data.

 Hard Disk : Hard disks are made of aluminum or other metal alloys which are coated on both sides with magnetic material. Unlike floppy disks, hark disks are not removable from the computer. To remain the storing capacity several disks

are packed together & mounted on a common drive to form a disk pack. A disk is also called a platter.
Magnetic Tape : Magnetic tape is a mass storage device. It‟s used as a back up storage. It‟s a serial access type of storage device. Its main advantage is that it stores data sequentially. Standard sizes are ½ inch or ¼ inch or 8mm & 3mm wide. Some Head names of tapes are: DAT (Digital Audio tape) & DLT (Digital Liner Tape) etc.

Optical Memory : Information is written to or read from an optical disk or tape using laser beam. Optical disks are not suitable memory storage units because their access time is more than that of hard disks. Their advantage is that they have very high storage capacity. Types of optical memory are: CD –ROM, CD-R, CD-RW, DVD-ROM, DVD-R and DVD-RW. Information on a CD-ROM is written at the time of manufacture.
CD-R/W of 700 MB are available.
A DVD-ROM is similar to CD-ROM. It uses shorter wave length of laser beam and hence, stores more data than CD-ROM.

Q.2. Explain about Modem.

Ans.: Modem is abbreviation for Modulator – Demodulator. Modems are used for data transfer from one computer to another through telephone lines. The computer works in digital mode, while analog technology is used for carrying massages across phone lines. Modem converts information from digital mode to analog mode at the transmitting end and converts the same from analog to digital at receiving end. Modems are two types :
(i) Internal Modem
(ii) External Modem

Q.3. What is Formatting?

Ans.: The process of magnetically mapping of a floppy is called formatting. Before storing the data on a floppy, it needs to be magnetically mapped, so that data can be stored in the right place. Every new floppy needs to be formatted before use. Formatting means, creating tracks & sectors on the floppy. Tracks are in the shape of circles on the floppy which divide it into various segments. The number of tracks depends upon the density of the floppy. In a high density floppy, up to 80 tracks can be created. If a floppy has 80 tracks with each track having 20 sectors, then the number of sector would be 1600.


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