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Why Use Cd's as Media Storage
CDs are now the major medium for circulation
of software. If you go to the computer store to
purchase a program, you’ll realize that
they no longer offer programs on diskette. Why?
That’s an easy question to answer. A diskette
can hold 1.44 MB of data. Consequently, a software
company would have to use more than a few diskettes
to hold a large program. Even with compression
technology, this can amount to 20 or more disks.
Conversely, a single CD can hold about 650 MB
of data, and it costs less then a dollar to make.
CD-roms are covered with aluminum to mirror light
and imprinted with a series of pits and flat areas.
Reading these pits or flats denote 0's or 1's.
A thin laser beam reads the pits or the flats
while the disk is spinning. Light reflects from
the flat surfaces, not the pits. The photo detector
reads what is reflected and sends the 0's and
1's to the CPU.
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