A compact disc or CD is a
laser read data storage device on which audio, video, or textual material can be stored.
Although it has been used primarily for music storage, it offers a huge potential as the medium for the storage of massive amounts of many types of information. Unlike the conventional phonograph record, the CD stores information in digital form. Two-channel sound signals are digitally sampled at a rate of 44,100 times per second per channel. Each sample is expressed as a binary number value consisting of 16 binary digits. The sampled digital values, along with error correction data, tracking codes, and cueing data are recorded on a digital tape, which is used to make compression-molded plastic discs 12 cm long in diameter, each covered by a thin, reflective metallic layer and protected by a clear plastic coating.
While the CD is playing, a low-powered laser beam reads the digital data through the reflective rear surface of the disc. The CD is an improvement over the conventional record and tape recording with its accurate frequency response, a complete absence of background noise, a wider dynamic range, and longer wear.
A CD-ROM is a text/graphics/sound/storage medium that is accessed through the CD-ROM drive in a computer. A DVD player plays movies like a VCR. Since its commercial introduction in 1982, the audio CD has almost completely replaced the phonograph disc for high-fidelity recorded music. Philips Electronics NV invented it and Sony Corporation in 1980. The CD has come a long technological way is still making its effect on technology today.