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Write a short note on CD/DVD.

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DVD (an abbreviation of digital video disc[5] or digital versatile disc)[6][7] is a digital optical disc storage format invented and developed in 1995. The medium can store any kind of digital data and is widely used for software and other computer files as well as video programs watched using DVD players. DVDs offer higher storage capacity than compact discs while having the same dimensions.

Prerecorded DVDs are mass-produced using molding machines that physically stamp data onto the DVD. Such discs are a form of DVD-ROM because data can only be read and not written or erased. Blank recordable DVD discs (DVD-R and DVD+R) can be recorded once using a DVD recorder and then function as a DVD-ROM. Rewritable DVDs (DVD-RW, DVD+RW, and DVD-RAM) can be recorded and erased many times.

DVDs are used in DVD-Video consumer digital video format and in DVD-Audio consumer digital audio format as well as for authoring DVD discs written in a special AVCHD format to hold high definition material (often in conjunction with AVCHD format camcorders). DVDs containing other types of information may be referred to as DVD data discs.

Etymology

The Oxford English Dictionary comments that, "In 1995 rival manufacturers of the product initially named digital video disc agreed that, in order to emphasize the flexibility of the format for multimedia applications, the preferred abbreviation DVD would be understood to denote digital versatile disc." The OED also states that in 1995, "The companies said the official name of the format will simply be DVD. Toshiba had been using the name ‘digital video disc’, but that was switched to ‘digital versatile disc’ after computer companies complained that it left out their applications."[8]

"Digital versatile disc" is the explanation provided in a DVD Forum Primer from 2000[9] and in the DVD Forum's mission statement

History

Development

There were several formats developed for recording video on optical discs before the DVD. Optical recording technology was invented by David Paul Gregg and James Russell in 1958 and first patented in 1961. A consumer optical disc data format known as LaserDisc was developed in the United States, and first came to market in Atlanta, Georgia in 1978. It used much larger discs than the later formats. Due to the high cost of players and discs, consumer adoption of LaserDisc was very low in both North America and Europe, and was not widely used anywhere outside Japan and the more affluent areas of Southeast Asia, such as Hong-Kong, Singapore, Malaysia and Taiwan.

CD Video released in 1987 used analog video encoding on optical discs matching the established standard 120 mm (4.7 in) size of audio CDs. Video CD (VCD) became one of the first formats for distributing digitally encoded films in this format, in 1993.[11] In the same year, two new optical disc storage formats were being developed. One was the Multimedia Compact Disc (MMCD), backed by Philips and Sony, and the other was the Super Density (SD) disc, supported by Toshiba, Time Warner, Matsushita Electric, Hitachi, Mitsubishi Electric, Pioneer, Thomson, and JVC. By the time of the press launches for both formats in January 1995, the MMCD nomenclature had been dropped, and Philips and Sony were referring to their format as Digital Video Disc (DVD).[12][13]

Representatives from the SD camp asked IBM for advice on the file system to use for their disc, and sought support for their format for storing computer data. Alan E. Bell, a researcher from IBM's Almaden Research Center, got that request, and also learned of the MMCD development project. Wary of being caught in a repeat of the costly videotape format war between VHS and Betamax in the 1980s, he convened a group of computer industry experts, including representatives from Apple, Microsoft, Sun Microsystems, Dell, and many others. This group was referred to as the Technical Working Group, or TWG.

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