A Compact Disc, known as CD, is an optical disc used for the digital storage of data, initially developed for audio files. The CD has been available on the market since October 1982 and remains, even today, the physical form of commercializing music. The technology was updated afterwards and adapted in order to include the write-only system, which allows the CD to be edited only once regarding the information it holds. It is called CD-R, but there are alternatives with the possibility to rewrite them – CD-RW. The other versions that have appeared are the video compact discs (VCD), photo-discs, as well as the ultra performing ones. Optical disks and their successive versions have known great success over years, so 200 billion units were sold in 2007 only. The physical side of this optical unit reaches 12 cm, even if there are other variations of it, like the classical minis (8 cm) or the ones with the size of a business card. Standard ones have an audio capacity of approximately 74 to 80 minutes, while the mini version only has 24 minutes; the business card CDs can get to maximum 6 to 14 minutes, with a capacity of storage of 100 Megabytes of information.
The short history of CDs
The first optical disk appeared in March 1979, being the first unit made inside a factory in Germany, after a few years of intense research made by the companies Philips and Sony. The launch came after the great fall Philips had concerning the video disk technology in 1978. This was one of the first products benefiting from the laser technology, being able to read the stored information without any physical contact. The study and development of the product had begun since 1969. During the 1970s, Philips began to work on what will be named ALP – Audiolong play – an audio system with the form of a disk, which would have been a true rival of the vinyl disks, taking advantage of the laser technology as well.
Lou Otters, the technical director of the audio division inside the company thought that the new dimensions of the CD had to be smaller than the vinyl’s and that they should have the capacity to store approximately one hour of music. Shortly, the two companies, Sony and Philips, announced their alliance concerning the manufacture and development of the new product. Concerning the name, the two giants of the electronic industry have opted for Mini Rack, MiniDisc and Compact Rack, until they decided on the name of Compact Disk, because of the sonority that reminded of the success of the compact cassette. In March 1979, Philips held a press conference in Eindhoven, Germany, to show the audio quality of the CD which, at that time, cost a small fortune (somewhere around 1200 Euros, regarding the actual value of money). The plan the company had was to develop an optic disk with a dimension of maximum 11,5 cm. Sony insisted that the entire 9th symphony of Beethoven had to fit on such a disk, reason why the size grew to 12 cm in diameter.
In 1980, Philips and Sony launched the “Red Book”, in which the standards concerning the CDs were described, as the two companies were focused on the design of the further players. In April 1982, Philips presented for the first time in the world the Compact Disc Player. It was released on the market together with a CD with the recording of the interpretation of the Alps Symphony belonging to Strauss interpreted by the Philharmonic Orchestra in Berlin, controlled by Herbert Von Karajan. Abba’s album “The Visitors” was next. At first, the labels were pretty reticent concerning this new technology, launching just over 1,000 albums; then, in less than two years. In 1985, the album “Brothers in Arms” of Dire Straits became the first CD to be sold in more than 1,000,000 copies, being the most successful album ever launched until then. The first artist who made the transition towards CD was David Bowie, in February 1985. In the next few years, 400 million copies were made in over 50 companies over the world. Once with the launch of the mp3, in 2000, CD sales registered a gradual loss, by approximately 20 per cent.
The CD was invented to become the follower of the vinyl disk and not the main means of data storage. In June 1985, the first CD-ROM appeared on the market, becoming part of the Personal Computer, while during the 1990s, Sony and Philips introduced the CDs which allowed the audio recording.
Physical details of CDs
The CD is made of a 1,2-mm thick disc, being made of plastic with a weight of approximately 16 grams. A very thin layer of aluminum is applied on the surface of the disc in order to make it reflective, another protective layer being added to prevent oxidation. A laser fascicle reads the disc, which reflects it in order to be read by the player.
CDs are sensitive enough to exposure and daily manipulation. The accumulation of dust can lead to the slowness of processing. The possibility to repair them in order to recover the data exists, with a substance similar to plastic or by polishing them carefully.