4

CD, CD-ROM,
CD-RW,DVD,
DVD-RAM,
DVD-ROMand
more…..

—Otmar Foelsche

The list of acronyms is getting
longerand longer and less
comprehensible. Allof the above
areshiny little discs of exactly the
same size that should be treated
with utmost respect, i.e. no coffee,
tea, chemicals, scratches, etc. They
areread witha laserbeam (or
severallaserbeams) and should
last forquite a while. The compact
audio disk, commonly called CD,
is themost familiar type of disk
containing about 74 minutes of
audio programming and playable
in CD-players at home, in cars, as
well as in most computers.

A CD-ROM contains data of the
typethat is stored on floppies, zip
disks, and hard disks. Its capacity
is huge — roughly theequivalent
of 450 HD floppies or a 650 MB

hard disk. Once data has been
moved to a CD-ROM it canonly be
read. It cannot be erased, it cannot
bechanged. It is simply there. If
the CD-ROM does not get
scratched the data can be expected
to remainundamaged forat least
thirty years — undernormal
storage conditions. CD-ROM,
therefore, is a “write once — read
many times” medium that is also
cheap: only about $.80 perdisk.
Producing a CD requires a special
writer/playerthat is often called a
“burner,” together with the most
popular software that is called
“Toast.”

A CD-RW is similar to a CD-ROM
but its data canbe erased and
rewritten about a thousand times.
It requires a special“writer/
player” that costs a little morethan
the standard CD player. The disks
cost about $10 to $15and the
prices arecoming down rapidly.

Players forCD-ROMs and CD-
RWs arenot always totally
compatible with all types of CDs
forvarious platforms, especially
older models. They also differ
dramatically in playback speed at
this timeprobably from2x to
about 52x. The higher thespeed
the more data can beread and
moved into the computer.

DVDs are rapidly replacing the
traditionalvideo tapes at home
and in institutions. They are
exactly the same size as CDs but
storedata ina different, much
denserway. They requirea special

player with video output and
various sound outputs tobe
connected to yourtelevision set or,
forthe technically minded, for the
home theater scene withfull
surround sound and more. Most
new computers now comewith a
player that can handle the
playback of alltypes of CDs as
well as of DVDs. ConsumerDVD
playback units canonly handle
playback of DVDs that arecoded
forourhemisphere. If you want to
play DVDs purchased in Spain,
France, or Japan, you are out of
luck—you willget a message on
the screen that says, “this DVD
cannot beplayed here.”But don’t
give up yet. Yourlate model
computerwill play it for you! You
can also cometo the Language
Resource Center and use a multi-
country DVD player. Consult wth
us beforeusing a foreign DVDin
your DVD player.

Most Macs now come with DVD-
ROM players. These DVD-ROMs
aresimilar to CD-ROMs but
handleabout 8 times thedata on
both sides. Some even come with
DVD-RAM drive. A DVD-RAM is
similarto a CD-RW and canbe
erased and rewrittenmanytimes
in a DVD-RAM drive.What a
DVD-RAM cannot do is the
production of a regularmovie
DVD. That stillrequires a very
special unit that is not availablefor
the consumermarket yet.
Obviously, the industryis not very
keen onproviding consumers with
the ability to copy DVDs without
loss of quality.
—continued on page 5