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A compact disc is a portable storage medium that can record, store and play back audio, video and other data in digital form. A standard compact disc measures 4.7 inches, or 120 millimeters (mm), across, is 1.2 mm thick, weighs between 15 grams and 20 grams, and has a capacity of 80 minutes of audio, or 650 megabytes ( MB) to 700 MB of data. A ...
Jul 28, 2023 · What is a compact disc? Compact discs are small plastic discs used to store digital information, such as music, video, etc. When was the compact disc invented? October 1982. How much did compact discs cost? $1,000 in 1982. What are compact discs used for? Compact discs were initially used for audio and data storage. What is an example of a ...
- Overview
- Physical characteristics
- Recording and replication
- Playback
compact disc (CD), a molded plastic disc containing digital data that is scanned by a laser beam for the reproduction of recorded sound and other information. Since its commercial introduction in 1982, the audio CD has almost completely replaced the phonograph disc (or record) for high-fidelity recorded music. Coinvented by Philips Electronics NV a...
A standard CD is 120 mm (4.75 inch) in diameter and 1.2 mm (0.05 inch) thick. It is composed of a clear polycarbonate plastic substrate, a reflective metallic layer, and a clear protective coating of acrylic plastic. The reflective metallic layer is where audio data is read in the form of minuscule (as short as 0.83 micrometre) depressions (pits) a...
The production of a CD begins with a digital tape master supplied by the recording studio (see also digital sound recording). The information on this tape is used to modulate a beam of light from a blue laser as it traces a spiral path on the surface of a spinning glass disc. The glass is coated with a photosensitive material that dissolves where it is exposed to laser pulses, forming the pits. This “glass master” is coated with a thin layer of nickel to form a “metal master,” and the metal master in turn is used to produce a number of “mothers.” Each mother serves as the master for several metal “stampers,” onto which molten polycarbonate is injected for molding into clear plastic discs. Each disc is exposed to a stream of vaporized or atomized aluminum, which forms the reflective layer, and is then coated with the protective acrylic layer. The entire production process is carried out under conditions of laboratory-like cleanliness and control.
By the mid-1990s, however, developments in computer technology advanced such that CD recording and replication could avoid the need for a digital tape master. High-quality sound recordings could be sent from the microphone or other device directly to computer programs whose digital files could be stored on the computer’s hard disk (or magnetic storage media) before being transferred to a CD.
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When a disc is inserted into a CD player, the disc’s track is scanned by a low-intensity infrared laser with a 1-micrometre-diameter focal point. In order for the laser to maintain a constant scanning rate, the disc’s rotation rate decreases from 500 to 200 revolutions per minute as the light beam spirals out from the disc’s centre. (Some CD player...
- The Editors of Encyclopaedia Britannica
The compact disc (CD) is a digital optical disc data storage format that was codeveloped by Philips and Sony to store and play digital audio recordings. It uses the Compact Disc Digital Audio format which typically provides 74 minutes of audio on a disc.
The aim of the Compact Disc Project was for the new format to eventually replace both the analogue video equipment and the Compact Cassette Tape. Both were popular technologies at the time, that had been in use and established for a good many years.
Mar 6, 2024 · The invention of the standard compact disc revolutionized the way music, data, and later video were stored and distributed, marking a significant leap from analog to digital storage media. Developed jointly by Philips and Sony, the CD format was finalized in 1982 and famously documented in the Red Book standard.
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Oct 19, 2023 · What Is A Compact Disc? Compact disc CD is a digital storage format for optical media jointly developed by Philips and Sony. The CD format was originally developed for storing and playing sound recordings but was later adapted for storing data. Data on a CD is encoded with the help of a laser beam that etches tiny indentations (or bumps, if you ...
