DVD+RW

DVD recordable and DVD rewritable refer to part of optical disc recording technologies. DVD optical disc formats that can be recorded by a DVD recorder, (written, "burned"), either or rewritable (write multiple times) format written by laser, as compared to DVD-ROM, which is mass-produced by pressing, primarily for the distribution of home video. DVD recordable is a general term that refers to both write-once and rewritable formats, whereas DVD rewritable refers only to rewritable formats.

Like CD-Rs, DVD recordables use dyes. Depending on the intensity of the laser, the reflective property of the dye on a particular spot will determine whether it is a peak or a valley representation from pressed DVD. Dyes give the data side of a disc a distinct color. Dyes are also the reason playback is not guaranteed. Their reflective properties are not as good as with stamped DVDs that commonly have aluminum as the reflective layer.

The larger storage capacity of a DVD-R compared to a CD-R is achieved through smaller pit size and smaller track pitch of the groove spiral which guides the laser beam. Consequently, more pits can be written on the same physical sized disc. In order to write smaller pits onto the recording dye layer, a red laser beam with a wavelength of 640 nm (for general use recordable DVD, versus a wavelength of 780 nm for CD-R) is used in conjunction with a higher numerical aperture lens. Because of this shorter wavelength, DVDs use different dyes from CDs to properly absorb this wavelength.

The "R" format DVDs can be written once and read arbitrarily many times. Thus, "R" format discs are suited to applications such as non-volatile data storage, audio, or video. This can cause confusion because the DVD+RW Alliance logo is a stylized 'RW'. Thus, a DVD+R disc may have the RW logo, but it is not rewritable.

According to Pioneer, DVD-RW discs may be written to about 1,000 times before needing replacement. RW discs are commonly used to store data in a volatile format, such as when creating backups or collections of files. They are also used for home DVD video recorders. One benefit to using a rewritable disc is if there are writing errors when recording data, the disc is not ruined and can still store data by erasing the faulty data.

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Wikipedia