Epson 10020 - Manual (Page 65)

To run an external command, MS-DOS must be able to locate
the file containing the command’s instructions. If it cannot
find the file, MS-DOS gives you an error message. If you have
the Apex 100\20, all the external files are on your hard disk
(drive C) in a directory named \DOS; so MS-DOS can find
any external command you need.
If you have the Apex 100 (with no hard disk), you must insert
the proper diskette to access an MS-DOS command. For
example, if you want to use the FORMAT program, you must
insert the Startup diskette in one of the diskette drives. Then
you can either log onto that drive and give the FORMAT
command or specify the appropriate drive when you enter the
command.
For example, if the Startup diskette is in drive A and you are
logged onto that drive, and you want to format a diskette that
is in drive B, you could enter the command as follows:
FORMAT B:
In this case, MS-DOS looks on drive A, the default drive, for
the file named FORMAT.COM and finds it there.
If you are logged onto drive B, however, you would need to
enter the command like this:
A:FORMAT B:
This tells MS-LXX to look on drive A for FORMAT.COM.
Entering an MS-DOS Command
To enter an MS-DOS command, you need to type the
command in the correct format. The command format provides
MS-DOS with the information needed to perform a task.
3-6 Using MS-DOS With Your Computer