CD-RW
The rewritable compact disc, known by the acronym CD-RW (from English Compact Disc - ReWritable, originally R and W were used as the attributes of the CD, which mean "read" and "write", reading and writing) is a type of digital support in optical disk used to store any type of information.
This type of CD can be burned multiple times, as it allows the stored data to be erased.
In 1996, it was developed jointly by the companies Sony and Philips; It began to be commercialized in 1997.
Technologies such as DVD have partly displaced this form of storage, although its use is still current.
In the CD-RW disc, the layer that contains the information is formed by a crystalline alloy of silver, indium, antimony and tellurium that presents an interesting quality: if it is heated to a certain temperature, when it cools it becomes crystalline, but if when heated it reaches an even higher temperature, when it cools it remains with an amorphous structure. The crystalline surface allows light to reflect well in the reflective zone while the amorphous structured zones absorb the light. Therefore, the CD-RW uses three types of light:
- Writing laser: used to write. Heats small areas of the surface so that the material becomesmorphic.
- Deleted laser: used to erase. It has a lower intensity than writing with what is achieved the crystalline state.
- Reading laser: used to read. It's less intense than erasing. It is reflected in crystalline zones and dispersed in themorphs.
In the beginning, the capacity of a CD-RW was 650 MB; currently the capacity is the same as that of a CD-R, 700 MB.