Cylinders versus tracks...

I generally teach it this way. A track is the path traced by a single head during a rotation of the spindle. A cylinder is the set of tracks traced by all the heads for a single position of the arm. Thus specifying the cylinder number specifies the position of the arm. Specifying the head number selects the desired track from the set in the cylinder. Track/surface is actually redundant since the combination of cylinder and head uniquely identifies a track. In other words, the track number implies the surface. As to the usage in the floppy world, I'd guess that it started with the old single-sided floppies. For them, a cylinder and a track were the same thing. Then for double-sided floppies, people tended to talk in terms of a track number on a side and didn't think in terms of cylinders at all. But on multiplatter disks, the concept of a cylinder becomes a lot more meaningful. Regardless of how many surfaces we have, it is the difference between our current cylinder number and the desired one that dominates the access time. BLS