Compact Disc-Rewritable

(C-D-R-W)

A type of compact disc that allows you to both read and write data. Basically, CD-RW discs can be treated like high-capacity floppy disks or removable hard disks. Each holds approximately 700MB. Be certain to check with the manufacturer; some CD-RW discs can only be read by a CD-RW drive while others can be read in a standard CD-ROM drive (CD-ROM drives made before 1997 may not be able to read the reduced reflectivity in a CD-RW disc).

Unlike CD-R discs where the laser records information by melting the substrate to form a pit, CD-RW discs record data by changing the phase state of crystals in the recording layer. At high recording temperatures the crystals take on a random orientation. At lower annealing temperatures (when the disc is "erased") the crystals return to their orderly state. The difference in crystal orientation shows up as a different reflection pattern on reading the disc.

[Spelling note: When applied to optical media you use "disc." When discussing magnetic media you use "disk."]

More Information

• CD-R FAQ