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