Since data density in the outermost track is less and data density is more in inner tracks so there are wastage of space on outer tracks.
To increase the capacity, the concept of zone is used instead of sectors. Each track is divided in zone of equal length and fix amount of data is stored in each zone. So the number of zones are less in innermost track and number of zones are more in the outermost track. Therefore, more number of bits are stored in outermost track. The disk capacity is increasing due to the use of zone, but the complexity of control circuitry is also more. The concept of sector and zone of a track is shown in the Figure 7.7.
