INT 17 - Printer BIOS Services

	For more information, see the following topics:

	INT 17,0   Print character
	INT 17,1   Initialize printer port
	INT 17,2   Read printer port status

	Status flags returned in register AH

	│7│6│5│4│3│2│1│0│  AH (status)
	 │ │ │ │ │ │ │ └────  time-out
	 │ │ │ │ │ └─┴─────  unused
	 │ │ │ │ └────────  1 = I/O error  (parallel pin 15)
	 │ │ │ └─────────  1 = printer selected/on-line  (parallel pin 13)
	 │ │ └──────────  1 = out of paper  (parallel pin 12)
	 │ └───────────  1 = printer acknowledgment  (parallel pin 10)
	 └────────────	1 = printer not busy  (parallel pin 11)

	- on the AT, XT 286, and PS/2 when the BIOS determines the printer
	  is busy,  INT 15,90  is executed
	- all printers do not return reliable status information;  bit 3 and
	  bit 7 are usually reliable.
	- all registers are preserved except AH