A CD is a little bit like an old fashioned vinyl record. Information such as music or even computer data, is stored in circles or tracks going around the CD. In a vinyl record, this was a groove that you could feel with your hand. On a CD, the tracks are not as visible although you can see rainbows. They are very small and instead of bumps like on a record, there are tiny little holes or pits.
This is the description I found in Compton's encyclopedia:
COMPACT DISC. High fidelity was redefined for audiophiles as soon as they heard the pure digital sound of a compact disc (CD). The sonic range of the plastic-coated CDs was so superior to the older "hi-fi" recordings that, by the early 1990s, long-playing (LP) vinyl discs became obsolete.
The production of a CD begins with a high-quality sound recording on magnetic tape (see Tape Recorder). The conversion of the constantly changing analog signal on the tape into a digital signal is what makes a CD different from an LP, the factor that enhances audio reproduction (see Electronics). To digitize the signal, it is converted into a series of electrical pulses.
After a master disc has been inscribed, the spiral series of pits and lands is impressed on the molded plastic CD base. A layer of reflective aluminum is applied to the label side and topped by a protective layer of plastic. The side opposite the label contains all the information on a CD.
I have given you a CD. These are computer CD's or CD-ROMs that used to contain computer data. I have scrapped off some of the label and reflective aluminum so you can see the different layers. Don't try to play these CD's.
Excerpted from Compton's Interactive Encyclopedia. Copyright (C) 1994, 1995 Compton's NewMedia, Inc.% % filename A220.DOC
ˆHow does a CD work and how are they made?
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