Compact Disc

The compact disc is a spin-off of the Laserdisc technology. Philips publicly demonstrated a prototype of an optical digital audio disc at a press conference called "Philips Introduce Compact Disc"in Eindhoven, The Netherlands on March 8, 1979. Three years earlier, Sony first publicly demonstrated an optical digital audio disc in September 1976. In September 1978, they demonstrated an optical digital audio disc with a 150 minute playing time, and with specifications of 44,056 Hz sampling rate, 16-bit linear resolution, cross-interleaved error correction code, that were similar to those of the Compact Disc introduced in 1982. A Compact Disc (also known as a CD) is an optical disc used to store digital data, originally developed for storing digital audio. The CD, available on the market since October 1982, remains the standard physical medium for sale of commercial audio recordings to the present day. A CD is made from 1.2 mm thick, almost-pure polycarbonate plastic and weighs approximately 16 grams. From the center outward components are at the center (spindle) hole, the first-transition area (clamping ring), the clamping area (stacking ring), the second-transition area (mirror band), the information (data) area, and the rim.