§  These are the memories which use high intensity light signals to store and read data from the memory device.

§  These memories are highly reliable, compact in size and inexpensive compared to their capacity.

§  These memories are circulars in shape and divided into tracks, normally contain large number of tracks.

§  These disks are normally sequential storage direct access medium that is one can access any of the track on these disk directly.

§  These are mainly three optical types of memory in the market.

·         CD ROM

·         WORM

·         DVD

CD ROM Disks:

§  This is the most popular types of optical disk in the market.

§  This was invented by Phillips Company; initially this memory was used for audio data storage, for recording and distributing music.

§  But later on CD become very popular medium to store and retrieve computer data because of its high capacity , high reliability and low cost.

§  Most of Compact Disks in the market are read-only type memories.

§  That is once the data is written on these disks then that cannot be altered.

§  CDs are inexpensive medium to store large amount of data, in fact one blank CD of approximately Rs/- 20 can store around 650 MB data, which is equivalent to storage of around 500 floppies.

§  CDs are used for storing all types of data like audio, video, text or any other type of business data.

§  Because of its low cost and high reliability, it is used as universal portable type of memory for distributing software and data from one place to other place.

§  Presently, CD’s manufacturer has also introduced the CD – R/W that is Compact Disk Rewriteable, which allows a CD to be written again and again like floppy.

§  CD- R/W is used just like the floppy but has the advantages of high capacity and more reliability than floppy.

§  With the popularity of internet and multimedia, the higher capacity storage mediums are required to share large volume of information in form of images and documents.

§  And CD and DVD storage mediums are playing very playing very important roles to share and exchange this information from one system to another.

§  In CD, a synthetic reflecting surface is used for data storage.

§  The data on CD is stored on multiple tracks with the help of laser light signals.

§  Over the years, The CD has gone through many technological changes; such as:

·         CD- ROM

·         CD – R/W

·         CD -RW

§  The popular companies that manufacture CD-ROM drive, CD- writer are Samsung, Creative, HP and LG.

WORM Disks:

§  These are optical memories known as Write Once Read Many time’s disks.

§  These memories are like CD-R and used for storage of historical data, permanently.

§  These disks can store approximately 200 MB data in the text and image data form.

§  WORM disk is no more a popular disk; it has been replaced by more popular optical laser disks known as CD – R and DVD – R.


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