Computer Dictionary/Compact Disc Recordable
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.