February 13, 2011

 CD-ROM



CD-ROM stands for Compact Disk Read Only Memory is a type of secondary storage or optical disc that users can read only but not write or erase. Philips and Sony companies invented Compact Disc in year 1982. CD-Rom is a WORM (Write Once Read Many times) device.  Typically they can store up to 600-700 MB of data or 70 minutes of audio, also store video, data, and text. The diameter of a Compact Disk is 4.7 inches and its thickness is 0.047 inches. A single Compact Disk equal to : 1500 - 5.25-inch floppy disks, 450 - 3.5 inch floppy disks and 274,000 pages of text.


Types of Compact Disks :

(1)  CD-ROM     :  
Compact Disk Read Only Memory (Write Once Read Many times)

(2)  CD-R       :  
(Compact Disc-Recordable) WORM disks for Well known technology

(3)  CD-RW      :  
(Compact Disc-ReWritable) Rewritable and erasable.

(4)  CD Extra    :  
For Multimedia purpose. Developed by Sony, Philips and Microsoft.

(5)  CD-DA      :  
(Compact Disk Digital Audio) Audio CD, Digital Audio Developed by Philips and Sony companies.

(6)  Photo CD      :  
Developed by Kodak and Philips companies.

(7)  Video CD      :  
Can hold approximately 70 minutes of recorded video.


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