Epson 386SX - Manual (Page 102)

If you do not have a hard disk, external commands are stored
on the set of working diskettes generated when you installed
MS-DOS. To use an external MS-DOS command, you must
insert the diskette containing that command into a diskette
drive. To find out which external commands are on which
diskettes, see the list of working diskette contents in your
MS-DOS Installation Guide.
For example, if you want to use the FORMAT command, you
must insert the Startup diskette into a diskette drive. Then you
can either log onto that drive and enter the FORMAT
command or specify the appropriate drive when you enter the
command.
For example, if you have two diskette drives and you want to
format a diskette that is in drive B, you need to insert the
Startup diskette into drive A, and log onto drive A. Then type
the following and press
Enter:
FORMAT B:
MS-DOS finds the file named FORMAT.COM on the current
drive.
If you are logged onto drive B, you need to type the following
and press Enter:
A:FORMAT B:
This tells MS-DOS to look on drive A for FORMAT.COM
because the current drive is drive B.
4-6 Using MS-DOS with Your Equity 386SX