The optical disk is a storage media from which data is read and to which it is written on by lasers. Optical disks can store upto 6 gigabytes (6 billion bytes). That figure is uch higher that that for portable magnetic media, such as floppies. there are four basic types of optical disks:
CD-ROM (Compact Disc-Read Only Memory)
This is a type of optical disk, capable of storing latge amounts of data up to 1 GB (although the most common size is 650 MB). A single CD-ROM has a storage capacity of 700 floppy disks.
The vendor stamps CD-ROMs with data and once stamped, they cannot be erased and filled with new data. to read a CD, you need a Cd-ROM player. all CD-ROMs are made to a standard size and format, so one can load any type of CD-ROM into any CD-ROM player. The data on a CD-ROM is permanent and can be read any number of times, but annot be modified.
WORM(Write Once Read Many)
WORM drives contain disks that you can record on only once. whatever you record on the disk remains there permanently. After that, the WORM disk behaves just like a CD-ROM. These drives are perfect for achieving large amounts of data and are frequently used by banks and accounting firms. To write data onto it, a laser beam of modest intensity is employed. IBM developed the 20GB WORM for its PS/2 system; it has a large storage capacity and a longer life. It is more reliable - the only drawback being the longer access time.
These are optical disks that can be erased and loaded with new data, just like magnetic disks. Both lasers and electromagnets are used to record information on a cartridge, the surface of which contains tiny embedded magnets.
DVD(Digital Video Disk)
DVD stands for Digital Video disk. The DVD is also a member of optical disk family. It has the same dimensions of a CD but has significantly higher storage capacity. DVDs are double-sided unlike simple CDs which are single sided. However, DVD drivers can read most of the CD media. Many types of DVDs are avaialble.
1) DVD ROM is just like a large CD-ROM, allowinng data and infrastructure material as well as audio and video. It requires a DVD-ROM drive installed in computer. DVD-ROM drivers can play DVD Video movies.
2) DVD-R is a write-once version for creating masters.
3) DVD-RAM is the rewritable DVD.
4) DVD-R/W is also a rewritable version but is more an extension to DVD-R than a competitor to DVD-RAM.
5) DVD-Video is a read-only DVD disk used in full lenght movies.