AT&T 6300 Programmer's Manual page 382

OPEN
Statement
Examples
7-226
10 OPEN "1",2,"INVEN"
10 OPEN "MAILlNG.DAT" FOR APPEND AS 1
If you write and install a device called FOO,
then the OPEN statement can be:
10 OPEN "DEVFOO" FOR OUTPUT AS #1
To open the printer for output, you could use
the line:
100 OPEN "LPT:" FOR OUTPUT AS #1
which uses the GWBASIC device driver. You
can use part of a pathname:
100 OPEN "DEVLPT1" FOR OUTPUT AS #1
This statement uses the MS-DOS device
driver.