What makes a cd rw rewritable

We just sent you an email to confirm your email address. Once you confirm your address, you will begin to receive the newsletter. Definitions by TechTerms. Tech Factor? First Name:. Last Name:. Thank You We just sent you an email to confirm your email address. Some of these packages lack features such as recording from an image, writing Video CDs and writing a disc with CD Text. Music lovers need a drive that has good CD-R write performance, fast audio extraction and support for CD Text the song title, artist name and other information that displays on CD Text-enabled players.

There are even more good CD-RW choices if you use your drive mostly for backing up data. When buying CD-R discs, you should treat the speed rating as your primary concern. This is especially true of the newer 20X and 24X drives, since reaction time is more important in these fast drives. Be wary of CD-R discs specifically labelled for music or audio use. These discs are stamped with a code identifying them as music CD-Rs.

Common minute, MB discs work most of the time because of the leeway built into the laser mechanism of many drives. Despite the popularity of 80 minute discs, the official industry standard for discs remains 74 minutes of audio run time and MB of data capacity. CD-RW drives only have a couple of years left in the mainstream. Already, the first bigger, better rewritable DVD digital versatile disc drives are hitting the market.

There are two problems, however. The other is a beta vs VHS style standards war. The DVR-A03 writes to a 4. Plus, its proponents claim that this format has even greater backward compatibility with home DVD players that is, ones you attach to your TV as opposed to your PC — though this remains to be seen.

Instead of dye or pits, these discs feature a layer of phase-change material. This material can exist in two different solid states: crystalline or amorphous. Most solids have a crystalline structure in which the atoms are close packed in a rigid and organized array. But some materials can have an amorphous state in which the atoms are organized not into arrays but randomly, as in a liquid. A common example of such a material is ordinary window glass, an amorphous form of silica.

The phase-change material can change from one phase to the other when it is heated and cooled. The material used is chosen because the two solid states reflect light differently. The amorphous state reflects less light than the crystalline state does. Therefore, by starting with a disc surface in the crystalline state, heating with the laser can change small spots to the amorphous state, which will appear dark upon playback. Heating the material with the laser beam above its melting point transforms it from crystalline to amorphous.

The rapid cooling of the spot causes the material to freeze in the amorphous state. These spots can then be erased in a process known as annealing. This is accomplished by heating the material to a lower temperature, which transforms it back to its crystalline state. Existing data can be overwritten by turning the laser on continuously to the erase power, which will erase any existing marks.

Switching the laser to a higher power, one sufficient to melt the material, enables the creation of a new mark. Once an area of the disc has been written to, it cannot be erased.

The recordable layer is an organic cyanine or pthalocyanine dye. Initially, the organic dye has high reflectivity. When the laser is applied in write mode, however, a chemical reaction occurs that makes that "pit" less reflective than the "land" around it.

During readout, the laser detects the difference in reflectivity between the "pits" and "lands" to read the data or music. CD-R discs are highly reflective--about 60 to 70 percent of light is reflected or bounced back to the photo detector or read laser.