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CD-R CD-recordable, a write-once optical-disk format designed to be readable by systems that can read CD-ROM disks. CD-R disks have a spiral track and a recording layer of a special cyanine or azo dye. There is a thin layer of gold or silver alloy coating the dye. In the writing process, the laser “burns” patches of the dye layer. These have different reflectivity and correspond to the pits on a CD-ROM disk. CD-R is a cheap and reliable method of data storage. Although the data cannot be erased, more data can be added later in multisession recording (although a multisession CD-ROM drive is necessary to read these added files; older CD-ROM drives only detect the first recording session). See also CD-ROM format standards.