Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Zone Bit Recording (ZBR) is used by disk drives to store more sectors per track on outer tracks than on inner tracks. It is also called Zone Constant Angular Velocity (Zone CAV or Z-CAV or ZCAV).On a disk consisting of concentric tracks, the physical track length may or may not be increased with distance from the center hub. Therefore, holding storage density constant, the track storage capacity likewise increases with distance from the center. ZBR is a compromise between CLV (which packs the most bits onto a disk, but has very slow seek times) and CAV (which has faster seek times, but stores fewer bits on a disk).Hard disk controllers implement VBR by varying the rate at which it reads and writes - faster on outer tracks. Some other ZBR drives, such as the 3.5" floppy drives in the Apple IIGS and older Macintosh computers, spin the medium faster when reading or writing inner tracks.