DVD-RW stands form Digital Versatile Disc - Rewritable. It allows the user to record and erase data multiple times on the disc. The specifications are available in Book F. Similar to CD-RW and DVD-R, DVD-RW can contain information such as video, text, audio, and computer data. DVD-RW disc can be played on any type of DVD playback device. It can hold up to 9.4 gigabytes of information compared to the 650 megabytes of information on a CD.
DVD-RW recording is similar to CD-RW recording. The polycarbonate substrate is the same. It has a special spiral groove to guide the laser when reading and writing. An alloy is present which can change back and forth from a crystalline form when exposed to a particular light. This alloy serves as the recording medium. When the alloy is heated to a particular temperature, it becomes crystalline when cooled. When heated to another higher temperature, the alloy will not hold its shape when cooled. It becomes amorphous. Thus, by using different intensity lasers, crystalline and non-crystalline areas are obtained. The crystalline layer will reflect the laser while other layers will absorb it. The differences are registered as binary data. However, the patterns created are less distinct than those of other normal CD are and DVD formats are. Thus they require a more sensitive device to playback. Two dielectric layers draw excess heat from the recording alloy.
