Transcript Compact Discs - Wentworth Institute of Technology

 Around
670.9 billion CDs have been sold
all over the world
 CD’s revolutionized the way that data
could be stored and moved
 DVDs replaced VHS
 CDs replaced Cassette Tapes for music
 Also they replaced floppy discs for data
storage
 Prices range from $1-$5
Starting
taking over both
audio and computer
programming market in the
1980’s
Referred to as color books
before CD’s
There was five original books
 Outlined
the specifications regarding CD
Digital Audio.
 This was the common CD used in stereo
systems, and was capable of holding up
to 99 tracks,
 Roughly able to hold 74 minutes of audio
information
 Read
Only Memory became the standard
for computer-based compact discs
 Computer system that had a CD-ROM drive,
could read this format.
 It was capable of holding around 650 million
bytes of data.
 CD-R's were developed under the same
standards
 CD-ROM discs uses aluminum in their
construction, the CD-R discs uses gold,
which makes color a distinguishing feature.
 Covered
CD-Interactive technology, is
used to synchronize both audio and data
tracks on a CD-ROM in order to provide
things such as full motion video
combined with interactivity.
 Published in 1986, Phillips Interactive
primarily marketed this technology.
 Outline
for the coming generation of
writable CD technology
 Primarily CD-E. (Compact Disc - Erasable)
 The technology is available today, but know
otherwise as CD-RW. (Compact Disc ReWritable)
 Much like a floppy disc or hard drive, data
can be written and rewritten to these discs,
allowing for a very large yet portable
medium of data storage.
 Video
compact discs, and contains the
standard of data compression that is used to
display large amounts of audio and video on
a home computer.
 This concept more or less morphed into
what is now known as DVD (Digital Video
Drives,)
 While the DVD was not compatible with the
standard CD-ROM drives used in
computers, it did achieve what the White
Book had outlined for the future.
When a compact disc is written, tiny rivets are made
in the surface of the disc called stripes or pits.
 The areas between these pits are called lands, which
together make up a pattern where data is written.
From there
 CD-ROM drives use a read head to interpret these
patterns, which is done by focusing a laser beam on
the surface of the disc.
 If the laser comes in contact with a pit, the light is
reflected off in all directions. However, if the light
comes in contact with a land, it reflects back into the
read head, triggering an electric impulse.
 Binary code is used to interept the rivets



1. First a thick, soft, clear plastic layer. This layer comprises
the majority of the CD's thickness and weight. It serves two
purposes. First, it protects the data layer from damage on the
play side.
Secondly it acts as a lens to focus the CD player's laser onto
the data layer so it can more easily read the data.
2. The data layer is where the music and any other
information is stored. It's the layer that the CD player "reads"
in order to create the music, graphics, etc. The data layer is
molded or pressed into the top of the clear plastic layer.

3. A metallic layer is located on top of the data layer. It
allows the disc to function like a mirror, reflecting the CD
player's laser back to the detector in the CD player after it
reads the data layer It's this layer that gives the CD's play
side a shiny appearance.
4. A thin, hard protective layer is an ultra-thin plastic
coating that is added to provide some protection for the
reflective and data layers, while also forming a surface upon
which the label information can be printed.
5. Finally the label layer is printed on top of the protective
layer. It contains the title, graphics, band and other
information to identify the contents of the disc.
the layers of a disc

 How
it is read
 CDs
truly revolutionized data storage and
uploading
 The materials are made to last and if
properly stored could last a lifetime
 The CDs revolutions is now a days being
over shadowed by the mp3 revolution
moving in which is much easier
 Pirating has made the sales of CDs go
down over the past decade