Compact Disc

Are compact discs compact enough for you?

A compact disc is a thin optical disc, used primarily to store digital information, and it is also commonly called a ‘CD’.
Compact discs are circular in shape, with a central hole, and are made of plastic, that is usually coated with aluminium or gold for reflecting the laser that ‘reads’ the disc, and then a layer of lacquer is applied for protection.
The storage space of compact discs usually has a maximum capacity of 700 MiB – mebibytes (734 MB – megabytes) of data, in the form of programs, media or information, which equates to approximately 80 minutes of audio.
The typical size of a compact disc is 12 centimetres (4.7 inches) in diameter, although they can be as small as 6 to 8 centimetres (2.4 to 3.1 inches) in diameter.
American James Russell was the inventor of the optical digital recording and playback concept that is used in compact disc technology, which he designed in 1966, and he received a patent for the system in 1970.

In 1979, the companies Philips and Sony, formed an unusual working relationship, using James Russell’s concept, to together develop a compact disc, and in 1982 the first CDs were manufactured, being the ABBA music album The Visitors.
A compact disc spins when it is placed in a CD player or drive, and as it does, it is read by a laser that interprets the miniscule indents, called ‘pits’, invisible to the naked eye, found on the plastic layer of the disc.
Compact discs were originally designed to emit sound, however, in the 1980s it was realised that the disc could be used for a variety of purposes, including the storage of computer data.
Compact discs are usually purchased in a protective sleeve, like a hard plastic case; a paper packet; or a soft plastic envelope.
By 2007, world sales of compact discs had reached 200 billion, although sales have decreased significantly in recent years, due to digital technology and streaming; and in the music industry, 2014 marked the first year CDs were outsold by streaming technology.

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