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A conventional CD will have a diameter of just 12 cm and about 80 minutes audio [link widoczny dla zalogowanych] data can be saved on it. Smaller CDs are also manufactured [link widoczny dla zalogowanych] for storing single songs (called CD singles). They are 8 cm in diameter and can save 24 minutes of audio data.
The major research and enhancement work was done by Phillips and Sony. One of the first CDs came in bazaar way back in the year 1982 and till date, remains one of the most widespread mode of audio recordings.

In 1979, Phillips and Sony launched off a joint optional group in order to devise a successful digital audio disc. After a year`s work and lot of experiments and consideration, the compact disc [link widoczny dla zalogowanych] was invented. No sole person can be said [link widoczny dla zalogowanych] to have invented it, a large group collectively invented the compact disc.
In August, 1982, the earliest CD for business purposes was manufactured in a Phillips factory in Germany. The first music track that was released on a CD was `The Visitors (1981) by ABBA`. Quickly after, in October [link widoczny dla zalogowanych] of the same year, the CD players from Sony also reached the markets. The event is often called as [link widoczny dla zalogowanych] `the Big Bang` in the domain of digital audio.

The new idea was an instant hit in the bazaar. Consumers were enthusiastic about the superiority of the audio on the CDs. The price of CD players sank really fast, as a result of which, the popularity increased even more.

A Compact Disc is a 1.2 mm thick polycarbonate plastic disc weighing around 16 grams. To make the surface reflective, a very thin layer of [link widoczny dla zalogowanych] aluminum is spread on one side of the disc. A film of lacquer is also spread to act as a protecting shield. The label is printed on the other side using normal printing process like offset or screen printing. The data is saved on a CD in form of an array of tiny serrations called pits that are arranged in a spiral track. A pit is just 500 nm wide and 100 nm deep and the length varies from 850 to 3500 nm.

The CDs are much more durable than the preceding formats of audio storage. However, they can be damaged a little from the environment factors and daily usage. The [link widoczny dla zalogowanych] data is a lot nearer to the label side, so more harm occurs if dents are made of the label. The logical format to store audio data on a CD is a 2-channel 16-bit PCM encoded data at a sampling rate frequency of 44.1 KHz. The sampling rate was [link widoczny dla zalogowanych] chosen directly as a result of the sampling rate [link widoczny dla zalogowanych] theorem of double frequency needed in [link widoczny dla zalogowanych] recordings. With [link widoczny dla zalogowanych] some more calculations, the exact sampling rate of 44.1 KHz was decided.
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