What Are The Optical Disks And Compact Disks?

Direct access optical disk provides high density storage of data and use principles of optics. They include compact audio disks used for music and video disks used for storing pictures and films.  These disks have a highly polished surface. Digital data is encoded in the form of tiny pits, visible only with a microscope.  These pits are burnt or pressed into a thing coating of metal or other material deposited on a disk. A 12 inch disk has been used to record sight and sound and sporting events. Compact disk is used to record high quality music.  The optical technology of the compact disk has been adapted to store and retrieve computer data. Such disks are called compact disk read only memory (CD-ROM).

Data is read from these optical disks by focusing a beam of laser light on the pit patterns. A pit surface is interpreted as 1 and non-pit surface as 0. Because the reading head does not rub against the disk surface so they are said to have indefinite life. The storage density of optical disk is enormous and access time is relatively fast. Just one CD-Rom disk stores about 550 mega byte. In addition to CD-ROM which is a prerecorded read only disk there are laser based writable optical storage devices. They are called write once read memory.