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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
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.
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-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.
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.
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.
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.
MD Data disks can be fully read-only, fully rewritable, or be a hybrid of the two, with a portion of a disk being read-only and while another is rewritable. With 140 MB disks, MD Data offered about 100 times as much storage capacity as ordinary diskettes, and more than its competitors like the Zip (100 MB), SuperDisk (120 MB), and EZ 135 (135 ...