The optical disk storage system includes a rotating disk coated with a diminished layer of metal that facilitates a reflective surface and a laser beam, which is used as a read/write head for recording information onto the disk. Unlike magnetic disk, the optical layer consists of a single long track in the form of a spiral shape. The spiral shape of the track produces the optical disk applicable for reading huge blocks of sequential information onto it, including music.
There are two types of optical disks which are as follows −
Compact Disk (CD) − The terminology CD used for audio stands for Compact Disks. For use in digital computers similar terminology is used. The disks used for data storage are known as Compact Disk Read-Only Memory (CD-ROM). A compact disk is a round disk of clear polycarbonate plastic, coated with a very thin reflective layer of aluminum. During the manufacturing process of this 4.8 inches disk, pits are created on the surface of the disk. The portions between these pits are called lands. A typical CD can store data up to 700MB. Such high storage capacity is only possible due to a very high data density.
There are three types of CDs which are as follows −
WORM disks − WORM means write once and read many. The audio CDs that purchase from the market are WORM disks which are recorded by the company and can be played many times.
CD-Recordable − The recordable disks can be written only once. To produce multiple copies of CD or CD-ROM, a CD-recordable drive is attached to a computer that allows us to create our CD. It can record data on this disk, the laser forms bump in the due layer.
CD-Rewritable − These are the compact disks, which can be recorded, erased, and then re-recorded. These disks are used to store files that are frequently modified. These disks also provide a good means for the transportation of data. Once the data is transferred to the destination, the contents are deleted from the disk to make it empty again.
DVD Disks − DVD is the latest product in the market. DVD-ROM is a high-density medium capable of saving a complete-length movie on an individual disk. Its size is equal to the size of a CD. DVD-ROM produces such high storage capacities by using both sides of the disk, by using unique data-compression technologies, and by using intensely small tracks for saving information.