CD-R and CD-RW CD-R is the term used to denote CD-Recordable media. CD-R discs are recorded permanently. Once information is written, it cannot be erased. Data can be added until the disc is full. CD-R is good for creating archived information that need not be changed, or for distribution, because the price of CD-R media has dropped rapidly in the last few years. CD-RW is the term used to denote CD-ReWritable media. CD-RW discs can be written to many times. CD-RW media is rated for one thousand different writes to the media. CD-RW is perfect for personal file storage or for creating reliable backups that can be added to as necessary, and even rewritten as your backup scheme requires. While CD-RW media is more expensive than CD-R media it has a lower cost per megabyte than other competing technologies, such as Magneto�Optical or even magnetic removable media drives. CD-RW drives are very versatile for transporting information to both older and newer CD-ROM and DVD-ROM drives. CD-RW media can be read by newer CD-ROM and DVD-ROM drives. These newer drives are known as Multi-Read (MR) drives. And even though CD-RW media cannot be read by older CD-ROM drives, the Sony CD-RW Recorder can write to CD-R media which can be read by standard CD-ROM drives and Audio CD Players.
How CD-R and CD-RW work CD-ROM drives (CD-R and CD-RW drives as well) read the one and zero bits by difference in reflectivity. Mass produced Compact Discs are created by stamping �pits� in the CD. These �pits� reflect differently than the �land� which is the area between �pits.� CD-R drives work by using a laser beam to heat the recording layer, causing a chemical reaction in that spot so CD-ROM players will see this as a �pit� and the unburnt area as �land.� CD-RW uses what is known as a �Phase Change� technology. In the CD-RW media is a substance which can be changed from an amorphous �mark,� that very closely resembles the pits of a stamped CD, to a crystalline state which resembles �land.� The laser beam of the Sony CD-RW Recorder Drive changes the crystalline state to the amorphous state by use of a laser to quickly heat the spot on the disc, forming a mark. To change the amorphous state back to the crystalline state, the laser beam uses a lower power setting to transition the mark back to the crystalline �land.� Performance The CD-RW Recorder drive is capable of writing CD-R discs at 8X speed and CD-RW discs at 4X (quad) speed. Quad speed or 4X means that the drive can write (also called record or burn) a CD-RW disc at 600 kilobytes per second. This rate allows the drive to record a full 650 megabyte CD-RW disc in about 18 minutes. At 8X speed the drive can write at 1200 kilobytes per second, or record a full 650 megabyte CD-R disc in only 9 minutes.
