1. Compact Disc Read-Write Compact Disc Rewritable Compact Disc Recordable CD-R A write-once version of CD-ROM. CD-Rs can hold about 650 megabytes of data. They are very durable and can be read by normal CD-ROM drives, but once data has been written it cannot be altered. Standard prerecorded CDs have their information permanently stamped into an aluminium reflecting layer. CD-R discs have a dye-based recording layer and an additional golden reflecting layer. Digital information is written to the disc by burning forming pits in the recording layer in a pattern corresponding to that of a conventional CD. The laser beam heats the substrate and recording layer to approximately 250 C. The recording layer melts and the substrate expands into the space that becomes available. Phillips: New Technologies http://www-us. sv. philips. com/newtech/cdrewritable. html. See also CD-RW and DVD-RAM.
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