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