CD-ROM is an optical disc that stores digital data. It uses pits and lands on its surface to store binary data as either ones or zeros that is read by a laser. A CD-ROM drive reads this data by focusing a laser on the spinning disc. While CD-ROMs can only read data and not write it, specialized drives can burn new CDs by using laser to heat and mark the disc's surface. CD-ROMs provide a portable way to store large amounts of data that can be read on different computers.

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3. CD-ROM
 CD-ROM stands for compact disk read-only memory.
It is an optical disc used to store digital data,orginally
developed for storing digital audio. The data stored on
CD-ROM can only be read. It can cannot be deleted
or changed. CD-ROM is a portable storage device.
The data can be transferred from one computer to
another easily by using CD-ROM.

4. CD Structure
 It is flat, round, portable metal disc, which is coated
with a thin metal or plastic or other material that is
highly reflective.
 It is usually 0.75 inches in diameter and less than one-
twentieth of an inch thick.

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6. CD-ROM DRIVE
 It is also called a CD-ROM player, a device that can
read information from a CD-ROM. CD-ROM players
can be either internal, in which case they fit in a bay,
or external, in which case they generally connect to
the computer's SCSI interface or parallel port.

8. Reading data from CD-ROM
 A CD-ROM drive reads digital data from a spinning
disc by focusing a laser on the disc’s surface.
 Some areas of the disc reflect the laser light into a
sensor, and other areas scatter the light.

9. Pits and lands
 The CD-ROM holds digital data.
 Data is stored in the form of lands and pits.
 Lands are flat areas on the metal surface.
 Pits are depressions or hollows.
Reading logic ‘1’Reading logic ‘0’

10. Reading Speed
 Reading speed is measured in kB/s
 Reading speed determines the transfer of data in one
second.
 1× or 1-speed which gives a data transfer rate of
150 kB/s in the most common data format.
 Maximum speed available today is 52x.

12. Writing Data On CD-ROM
 A laser is used to heat a chemical dye in the disc to
create marks that will be read as data.
 As marks (pits) are created through burns, this
process is also referred as burning.
 Burning a CD is comparatively slower than reading it.
 Maximum burning speed is 32x.

13. Tracks and Sectors
 For burning, the first process is to format a blank CD.
 CD-ROM drive creates a set of concentric rings, called
tracks on each side of CD.
 Tracks are divided into short segments called sectors.
 Sectors are where data is stored physically.
Tracks

14. File System
 The format of the CD (file system) describes how the
data is stored on the CD.
 The earliest file system was High Sierra Standard.
 The ISO 9660 format is now the most common
format.

16. Storage Capacity of CD-ROM
 Storage capacity is the maximum limit of data storage
on a CD.
 A standard compact disc can store 650 MB of data or
about 70 minutes of audio.
 A new generation of compact disc, however, can hold
700 MB of data or 80 minutes of audio.

17. Advantages of CD-ROM
 It is the least expensive way to store
large amounts of data and information.
 CD-ROM disks are durable and easy to
handle.
 Information can be stored on CD-ROM
for many years.

18. Disadvantage Of CD-ROM
 The data cannot be edited.
 It retrieves data and information more slowly
than magnetic disks.

19. Summary
 Compact Disk is a type of optical storage.
 It holds data through physical marks.
 Its is played in a CD-Player, and is read at different
speeds.
 Files system is required to write data on CD by
different methods.
 CDs are compact storage devices that can be moved
from on place to another easily.
 There is always a doubt in their durability.

20. References
 www.ecarta.com
 www.howstuffworks.com
 www.kioskea.com
 www.wikipedia.org
 www.answers.com
 www.ehow.com
 http://www.desktopclass.com