Concept

CD-R

Summary
CD-R (Compact disc-recordable) is a digital optical disc storage format. A CD-R disc is a compact disc that can be written once and read arbitrarily many times. CD-R discs (CD-Rs) are readable by most CD readers manufactured prior to the introduction of CD-R, unlike CD-RW discs. Originally named CD Write-Once (WO), the CD-R specification was first published in 1988 by Philips and Sony in the Orange Book, which consists of several parts that provide details of the CD-WO, CD-MO (Magneto-Optic), and later CD-RW (Re Writable). The latest editions have abandoned the use of the term CD-WO in favor of CD-R, while CD-MO was rarely used. Written CD-Rs and CD-RWs are, in the aspect of low-level encoding and data format, fully compatible with the audio CD (Red Book CD-DA) and data CD (Yellow Book CD-ROM) standards. The Yellow Book standard for CD-ROM only specifies a high-level data format and refers to the Red Book for all physical format and low-level code details, such as track pitch, linear bit density, and bitstream encoding. This means they use Eight-to-Fourteen Modulation, CIRC error correction, and, for CD-ROM, the third error correction layer defined in the Yellow Book. Properly written CD-R discs on blanks of less than 80 minutes in length are fully compatible with the audio CD and CD-ROM standards in all details including physical specifications. 80-minute CD-R discs marginally violate the Red Book physical format specifications, and longer discs are non-compliant. CD-RW discs have lower reflectivity than CD-R or pressed (non-writable) CDs and for this reason cannot meet the Red Book standard. Some hardware compatible with Red Book CDs may have difficulty reading CD-Rs and, because of their lower reflectivity, especially CD-RWs. To the extent that CD hardware can read extended-length discs or CD-RW discs, it is because that hardware has capability beyond the minimum required by the Red Book and Yellow Book standards (the hardware is more capable than it needs to be to bear the Compact Disc logo).
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