Epson Equity 286 PLUS - Manual (Page 211)

Caution
The hard disk format procedure destroys any data on your
hard disk.
You may want to reformat a hard disk if you have a serious
problem with the drive. However, before formatting a disk with
data on it, try every other recovery procedure described in your
MS-DOS Reference Manual. Then back up all the data on the
disk before you begin.
Note
If you do not enter a bad track list before you format the disk,
the format program analyzes the surface of the hard disk to
determine the bad tracks.
Media Analysis
This test identifies the bad tracks on the hard disk by analyzing
the surface of the disk to find them. The program uses three
different bit patterns; formatting the disk, marking the bad
tracks, and displaying the bad track list.
Caution
The Media analysis test destroys any data on your hard disk.
Perfoming System Diagnostics C-27