Users can read data from the CD but cannot burn/write their information on CD.
CD Writer
Users can read and write data to and from the CD.
DVD-ROM
Users can only read data from the CD and DVD.
DVD Writer
Users can read and write data from both CD and DVD.
Working
Consists of three motors.
First to inject and eject the tray, second for spinning the CD and third to move the laser beam back and forth.
Uses Optical-disk technology where a laser beam alters the surface of a plastic or metallic disk to represent data.
Unlike to hard disk, which uses magnetic charges to represent 0 and 1, optical disks uses reflected light.
On disc surface (CD or DVD) 1's and 0's are represented by flat areas called lands and bumpy areas called pits.
To read a disc, a laser of tiny beam of light is emitted on the surface area.
This surface area reflects the light, and amount of reflected light determines whether the area represents a 0 or a 1.
To write on the disc a tiny laser of beam of light is emitted to heat the layer made-up of organic dye or metallic alloys to form pits. And these alternating lands and pits form the data.
For CD-R it is heated upto approximate 200°C and for CD-RW approximate 700°C.
As read and write operation does not touches the surface of the disc, there is no friction and no wear or risk of disc crashing.