Compact Disc Rewritable
<storage> (CD-RW) A rewritable version of CD-ROM. A CD-RW drive can write
about 650 megabytes of data to CD-RW media an unlimited number of times. Most
CD-RW drives can also write once to CD-R media.
CD-RW media cannot be read by CD-ROM drives built prior to 1997 due to the
reduced reflectivity (15% compared to 70%) of CD-RW media.
CD-RW drives and media are currently (1999) more expensive than CD-R drives and
media. CD-R is sometimes considered a better technology for archival purposes as
the data cannot be accidentally modified or tampered with, and encourages better
archival practices.
Standard prerecorded CDs have their information permanently stamped into an
aluminium reflecting layer. CD-WR discs have a phase-change recording layer and
an additional silver (aluminium) reflecting layer.
A laser beam can melt crystals in the recording layer into a non-crystalline
amorphous phase or anneal them slowly at a lower temperature back to the
crystalline state. The different reflectance of the areas make them appear as
the 'pits' and 'lands' of a standard CD.
Phillips: New Technologies.
See also CD-R and DVD-RAM.
(1999-08-01)
Nearby terms:
Compact Disc Read-Only Memory « Compact Disc
Read-Write « Compact Disc Recordable « Compact
Disc Rewritable » compaction » compactness
preserving » Compaq Computer Corporation
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