CD-R (Compact Disc, Record able) is a type of WORM (Write Once, Read Many) compact disc, which allows recording on a disc once. The CD-R was made known by Philips and Sony in their 1988 description document, the Orange Book. Prior to the release of the specification book, available CDs were CD-Digital Audio to be played in CD players, and CD-ROM, to be played in PCs’ CD-ROM drives. After the Orange Book, any computer user could create their CDs from their system.
Like other CDs, CD-Rs are made of a poly carbonate plastic, a thin protective coating, and a thin reflective metal coating. In CD-R, however, a layer of organic polymer dye between the metal and poly carbonate layers acts as the recording medium.
The make-up of the dye is transformed permanently by exposure to a particular frequency of light. Some CD-Rs have additional protective layer to ensure that they are less vulnerable to damages from scratches. Since the data unlike the ones on common CDs is closer to the label side of the disc.
A CD-R disc usually holds 650 MB or 74 minutes of data, although some can accommodate 700 MB or 80 minutes of information. With a compatible CD-R drive and packet writing software, it is possible to store data on a CD-R in the same manner that one can store data to a floppy disk.
However, it is not possible to delete files and reuse them since each part of the disk can only be written once. The Re writable CDs use an alloy layer – instead of the dye layer – which can be changed to and from a crystalline state repeatedly.