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 15.00mm diameter central hole that accommodates the rotating center spindle of the drive. Beginning at the edge of the center hole (radius 7.50mm) and proceeding outward, a CD-R disc is divided into the following areas:
The Clamping Area is that portion of the disc that the drive spindle grasps to rotate the disc. On a pressed CD, this area extends from radius 7.50mm to 23.00mm. On a writable CD, this area occupies radius 7.50mm to 22.35mm.
The System Use Area (SUA) is present only on writable discs, occupies radius 22.35mm to 23.00mm, and can be thought of as equivalent to the boot sector of a hard disk. The SUA contains data that tells a CD drive or player what kind of information is stored on the disc, where it is located, and what format it uses. The SUA is inside the radius readable by standard CD-ROM drives and CD players, so only CD recorders can read and write to this area. The SUA is divided into two subareas:
The Optimal Power Calibration Area (OPCA), often called the Power Calibration Area (PCA) for short, is used by the CD writer as a testing area to decide the best write schema to use when writing to that disc. Each time you insert a disc into a CD-R drive, the drive fires its writing ...