文档介绍：How CDs Work
by Marshall Brain
CDs and DVDs are everywhere these days. Whether they are used to hold music, data or
computer software, they have e the standard medium for distributing large quantities of
information in a reliable package. Compact discs are so easy and cheap to produce that America
Online sends out millions of them every year to entice new users. And if you have puter
and CD-R drive, you can create your own CDs, including any information you want.
In this article, we will look at how CDs and CD drives work. We will also look at the different forms
CDs take, as well as what the future holds for this technology.
Understanding the CD
As discussed in How Analog and Digital Recording Works, a CD can store up to 74 minutes of
music, so the total amount of digital data that must be stored on a CD is:
44,100 samples/channel/second x 2 bytes/sample x 2 channels x 74 minutes x 60
seconds/minute = 783,216,000 bytes
To fit more than 783 megabytes (MB) onto a disc only inches (12 cm) in diameter requires
that the individual bytes be very small. By examining the physical construction of a CD, you can
begin to understand just how small these bytes are.
A CD is a fairly simple piece of plastic, about four one-hundredths (4/100) of an inch ( mm)
thick. Most of a CD consists of an injection-molded piece of clear polycarbonate plastic.