An optical disk drive is a storage medium from which data is read and to which it is written by lasers. Optical disks can store much more data, up to 6 gigabytes (6 billion bytes), than most portable magnetic media, such as floppy disks.
There are several basic types of optical disks:
- CD-ROM : Like audio CDs, CD-ROMs come with data already encoded onto them. The data is permanent and can be read any number of times, but CD-ROMs cannot be modified.
- WORM : Stands for write-once, read -many. With a WORM disk drive, you can write data onto a WORM disk, but only once. After that, the WORM disk behaves just like a CD-ROM.
- CD-R: Stands for Compact-Disc Recordable, which can be written to once (aside from multisession writing).
- CD-RW: Stands for Compact-Disc Rewriteable, which behave similar to CD-R but can be erased to create a new blank disk.
- DVD: A Digital Versatile Disc, which allows storing up to 4.7 GB. May appear as Double-Layer to contain 8.5 GB, and can even be double-sided to double the capacity once again.
- DVD-R: A recordable version of DVDs.
- DVD-RW: A rewritable version of DVDs.
These three technologies are not compatible with one another; each requires a different type of disk drive and disk. Even within one category, there are many competing formats, although CD-ROMs are relatively standardized.