How does a Zip drive store so much more data than a floppy drive?

The 1.44-megabytefloppy disk drivesthat use 3.5-inch diskettes have been around for about 15 years. At the time of their introduction, they seemed like a miracle -- they were smaller than the standard 5.25-inch disks, but they held more data!

Here are some of the parameters that determine how much data a floppy disk can hold:

Two important things to notice are thelow number of trackson the disk and thefixed number of sectorsper track. Neither one of these techniques makes very good use of the surface of the disk.

The main thing that separates a Zip disk from a floppy disk is themagnetic coatingused on the disk. On a Zip disk, the coating is much higher quality (seeHow Tape Recorders Workfor some discussion on magnetic coatings). The higher quality coating means that a Zip disk read/write head can be significantly smaller than a floppy disk's (by a factor of 10 or so). Thesmaller head, combined with a head positioning mechanism similar to that used in ahard disk, means that a Zip drive can pack thousands of tracks per inch on the track surface. Zip drives also use avariable number of sectorsper track to make the best use of disk space. All of these things combine to create a floppy disk that holds a huge amount of data!