Epson 20 - Manual (Page 170)

The text data includes all the characters commonly used by programs
that require foreign languages or graphic characters. If your printer
prints different characters than you see in the illustration, you may
need to take care with certain software. The bit-image data is sent to
the printer using a command (ESC K) compatible with Epson and
IBM printers. If this pattern is printed correctly, you can use the
MS-DOS GRAPHICS command to print out copies of graphics
screens.
Hard Disk Drives and Controller Check
Use this option to test the performance of the hard disk drive(s)
installed in your computer. If any errors occur, have your dealer or
service center check and service the drive. When you select option 17
from the DEVICE LIST, you see this menu:
HARD DISK DRIVE(S) AND CONTROLLER CHECK MENU
l - Seek check
2
- Write,
read check
3
- R e a d , v e r i f y c h e c k
4 - R u n a l l a b o v e c h e c k s
0 - Exit
Enter selection number:
C-26 Performing System
Diagnostics