The following quote is from page 4-27 of the MSCP Basic Disk Functions
Manual which is part of the UDA50 Programmers Doc Kit manuals:

As stated above, the host area of a disk is structured as a vector of
logical blocks.  From a performance viewpoint, however, it is more
appropriate to view the host area as a four dimensional hyper-cube, the
four dimensions being cylinder, group, track, and sector.
	. . .
Referring to our hyper-cube analogy, the set of potentially accessible
blocks form a line parallel to the track axis.  This line moves
parallel to the sector axis, wrapping around when it reaches the edge
of the hyper-cube.