Tandy 1000 Programmer's Reference Manual page 209

Chapter
6 I BIOS Services
Line Printer
These routines provide an interface
to
the parallel line printer.
This device is labeled "PRN' in the device list maintained by the
operating system.
Software Interrupts:
17 hex (23 dec)
Function Summary:
AH
=
0: Print Character
AH
=
1: Reset Printer Port
AH
=
2: Get Current Printer Status
Function Descriptions:
Print Character
Print a character.
Entry Conditions:
AH
=
0
AL
=
character to print
DX
=
printer to be used (0-2)
Exit Conditions:
OAH
=
printer status; see Get Current Printer Status (AH
=
2)
below
(If bit 0 is set, the character could not be printed be-
cause of a timeout error.)
Reset Printer Port
Reset (or initialize) the printer port.
Entry Conditions:
AH
=
1
DX
=
printer to be used (0-2)
Exit Conditions:
AH
=
printer status/ see Get Current Printer Status (AH
=
2)
below
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