Writable CD Formats

The physical and logical format used by writable CDs is defined in the rainbow books described in the CD-ROM chapter. The following sections provide an overview of how data is physically and logically stored on writable CDs. For further detail, refer to the rainbow books.


CD-R discs are manufactured with a pregroove track, which is 600 nanometers (nm) wide with a 1,600nm pitch. The pregroove includes an impressed timing wobble of ±3 nm radial excursion at 22.05 KHz, with an FM carrier modulated at 1 KHz superimposed on the pregroove. This modulation provides an absolute clock signal (called absolute time in pregroove, or ATIP) which provides an absolute location reference for any sector on the CD-R disc. Absolute addresses on the CD-R disc are specified in the form HH:MM:SS using ATIP information. Audio CDs are addressable in this manner with resolution of one second (75 sectors). Data CDs are addressable to the individual sector level.

Physical Formats

Because they must be readable in a standard CD-ROM drive or CD player, writable CDs use a physical format nearly identical to pressed CDs. The dimensions of a CD are 120.00mm in diameter (60.00mm radius) with a 15mm diameter central hole, which accommodates the rotating center spindle of the drive. Beginning at the edge of the center hole (radius 7.50mm) and proceeding outwards, a CD-R disc is divided into the following areas:

Clamping Area

The Clamping Area is that portion of the disc that the drive spindle ...

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