What Is A CD?
The compact disc, abbreviated to CD, is a type of optical disc. Used to store digital data, it has its roots as a audio storage device, before it was developed for other uses. CD's still remain as the main medium for audio storage, and can hold up to 80mins of audio data.
Later on CD-ROM and rewritable formats like CD-R and CD-RW were developed complement the increasing need for portable data storage.
An optical disc drive is needed to read CD's.
Working Mechanism Of A CD
How Is The Data On A CD Read?
Once the CD is in the CD-drive, a drive motor will spin the CD and its speed will depend on which area of the CD it is reading. After which a laser is directed onto small bumps on the CD. The laser light is then reflected back to a lens and is converted to data and data blocks before it is sent to the computer of DAC (for audio CD).
How Does The CD Write?
To write to CD', the proper CD's (CD-R, CD-RW) and drive are needed.
Recordable CD's, there's a layer of dye between the polycarbonate plastic and aluminum. This dye is manipulated, or rather, heated with a laser, to create reflective and non-reflective areas. These heated bumps are non-reflective (the non-heated are reflective in comparison). Thus, although CD-R's do not have bumps like CD's, it can still be read and like a CD.
In a rewritable disc (CD-RW), instead the dye, a phase change compound is used. The compound can be "reset" so that data can be written over and over again. The compound works like the CD-R dye, where it is made into reflective and non-reflective blocks to represent data.
