Today, DVDs are beginning to supplant CDs as a medium to deliver huge
quantities of data or software. Engineers quickly shrunk DVD players to
laptop size, and were almost as fast coming up with several versions of
recordable DVD systems, called DVD-Rs.And most recently, laptops began
arriving with drives that could read both CDs and DVDs, and record either
CD-Rs or DVD-Rs or both.
Seeing CD Devices ........................................................................................
So, what can you do with a CD or DVD that you can’t do with a floppy disk
drive?
Install a huge operating system from one disc.
Install an office suite (word processor, spreadsheet, e-mail manager, cal-
endar, and other applications).
Play incredibly advanced computer games and simulations that reside
on a CD or DVD without eating up valuable space on the hard drive.
Offer access to huge encyclopedias, dictionaries, maps, and other data
that would not be cost effective to permanently store on a hard drive.
Record downloaded and copied (legally, of course) music to a CD that
can be played on a computer or on a Walkman or other portable music
player.
Create a backup copy of essential data as an archive.
Produce movies and digital photo slideshows and complex PowerPoint
presentations to take on the road for clients and meetings.
How a CD works..................................................................................
CDs are manufactured in a factory by pressing a metal master into a soft plas-
tic disk to imprint a pattern of pits and lands,or flat areas. The difference
between the two can be interpreted as 0s and 1s of digital data. Today’s CDs
can hold as much as 800MB of data, although some drives are happier with
slightly less ambitious recording schemes that store 600–700MB.
To read the disk, the CD player shines a focused laser beam of light onto a
small section of the spinning disk; light reflects back from the flat surfaces
but is absorbed or deflected by the pits. A photo detector reads the on and
off light flashes to a signal that is converted to 0s and 1s.
In addition to the technical elegance of a CD, the concept is extremely attrac-
tive to marketers because the discs are so very inexpensive to manufacture.
The first copy — the master— is the biggest expense but once the produc-
tion line is up and running, each disc costs only a few pennies to make.
Chapter 9: Going Round and Around: CD and DVD Drives .......................................
