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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.
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.
In optical storage, three types of storage are usually recognized, and given customary abbreviations: read-only ("ROM"), Write once ("R") and read/writable ("RW", or for Blu-ray, "E" for "erasable"). Examples: CD-ROM represents the CD format, in its pre-recorded "read only" use; DVD+R represents a DVD "+" disc which can be written once only
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.
Media technologies vary, for example, M-DISC media uses a rock-like layer to retain data for longer than conventional recordable media. While being read-only compatible with existing DVD and Blu-ray drives, M-DISC media can only be written to using a stronger laser specifically made for this purpose, which is built into fewer optical drive models.
Rewritable media is typically used in archive applications where the stability and longevity of optical media are important, but archive records change on a relatively frequent or discretionary basis. Rewritable media is typically used in archive environments where data needs to be deleted or media capacity re-used. True write once
Prior to CD-R, Tandy Corporation had announced a rewritable CD system known as the Tandy High-Density Optical Recording (THOR) system, claiming to offer support for erasable and rewritable discs, made possible by a "secret coating material" on which Tandy had applied for patents, [6] and reportedly based partly on a process developed by Optical ...