Epson 386SX - Manual (Page 105)

You can also use the Setup program on your Reference
diskette to set the correct time and date, See “Setting the
Real-time Clock” in Chapter 2 for instructions.
Creating and Managing Files
All your data and programs are stored in files on disk. A data
file contains information, such as words, numbers, or pictures. A
program file contains coded instructions that the computer can
understand and execute.
The kind of file you create depends on the MS-DOS command
or application program you use to create it. In general, a data
file that you create using an application program is stored in a
special format. If you use a different application program to read
that file, you may encounter problems.
When you create a file, you need to give it a name. The name
must be in the format MS-DOS requires.
Naming Files
Each file must have a unique name so that you can retrieve it
when you need to. The name consists of two parts: the filename
and the extension (which is optional).
The filename can be up to eight characters long. Create a
filename that identifies the information the file contains. You
can use any characters or numbers except for blank spaces and
the following symbols:
Using MS-DOS with Your Equity 386SX 4-9