CD-R

A CD-R (Compact Disc-Recordable) is a variation of the Compact disc invented by Philips and Sony. CD-R is a Write Once Read Many (WORM) optical medium, though the whole disk does not have to be entirely written in the same session.

CD-R retains a high level of compatibility with standard CD readers, unlike CD-RW - which can be re-written, but is not capable of playing on many readers, and also uses more expensive media.

History
The CD-R, originally named CD Write-Once (WO), specification was first published in 1988 by Philips and Sony in the 'Orange Book'. The Orange Book consists of several parts, furnishing details of the CD-WO, CD-MO (Magneto-Optic), and CD-RW (ReWritable). The latest editions have abandoned the use of the term "CD-WO" in favor of "CD-R", while "CD-MO" were very little used. Written CD-Rs and CD-RWs are, from a technical standpoint, fully compatible with the Audio CD (Red Book) and CD-ROM (Yellow Book) standards, although some hardware compatible with Red Book CDs may have difficulty reading CD-Rs and especially CD-RWs. They use Eight-to-Fourteen Modulation, CIRC error correction plus the third error correction layer defined for CD-ROM.

CD-R recording systems available in 1990 were similar to the washing machine-sized Meridian CD Publisher, based on the two-piece rack mount Yamaha PDS audio recorder costing $35,000, not including the required external ECC circuitry for data encoding, SCSI hard drive subsystem, and MS-DOS control computer. By 1992 the cost of typical recorders was down to $10–12,000, and in September 1995 Hewlett-Packard introduced its model 4020i manufactured by Philips, which at $995 was the first recorder to cost less than $1000.

The dye materials developed by Taiyo Yuden made it possible for CD-R discs to be compatible with Audio CD and CD-ROM discs.

Initially in the United States, there was a market separation between "music" CD-Rs and "data" CD-Rs, the former being several times more expensive than the latter due to industry copyright arrangements with the RIAA.Physically, there is no difference between the discs save for the Disc Application Flag that identifies their type: standalone audio recorders will only accept "music" CD-Rs to enforce the RIAA arrangement, while computer CD-R drives can use either type of media to burn either type of content.