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As of 2021, multiple consumer-oriented, optical-disk media formats are or were available: Compact Disc ("CD"): digital audio disc CD-R: write once read many (WORM) CD; CD-RW: rewriteable CD; DVD: digital video disc DVD-R: WORM DVD defined by the DVD Forum; DVD-RW: rewritable DVD defined by DVD Forum; DVD+R: WORM DVD defined by the DVD+RW Alliance
CD-RW (Compact Disc-Rewritable) is a digital optical disc storage format introduced by Ricoh in 1997. [1] A CD-RW compact disc (CD-RWs) can be written, read, erased, and re-written. CD-RWs, as opposed to CDs, require specialized readers that have sensitive laser optics.
The preservation of optical media is essential because it is a resource in libraries, and stores audio, video, and computer data. While optical discs are generally more reliable and durable than older media types, (magnetic tape, LPs and other records) environmental conditions and/or poor handling can result in lost information.
DVD recordable and DVD rewritable are a collection of optical disc formats that can be written to by a DVD recorder and by computers using a DVD writer.The "recordable" discs are write-once read-many (WORM) media, where as "rewritable" discs are able to be erased and rewritten.
For rewritable CD-RW, DVD-RW, DVD+RW, DVD-RAM, or BD-RE media, the laser is used to melt a crystalline metal alloy in the recording layer of the disc. Depending on the amount of power applied, the substance may be allowed to melt back (change the phase back) into crystalline form or left in an amorphous form, enabling marks of varying ...
CD-R, DVD-R, and DVD+R discs receive the dye layer after pressing but before metallization. CD-RW, DVD-RW and DVD+RW receive a metal alloy layer sandwiched between 2 dielectric layers. HD-DVD is made in the same way as DVD. In recordable and rewritable media, most of the stamper is composed of grooves, not pits and lands.
Various forms of optical media, mostly disk form, competed with magnetic recording through most of the 1960s and 70s, but never became widely used. It was the introduction of semiconductor lasers that provided the technology needed to make optical storage more practical in both storage density and cost terms.
Retail recordable/writable optical media contain dyes in/on the optical media to record data, whereas factory-manufactured optical media use physical "pits" created by plastic molds/casts. As a result, data storage on retail optical media does not have the life-span of factory-manufactured optical media.