Bitfields for printer status:
Bit(s)	Description	)
 7	not busy
 6	acknowledge
 5	out of paper
 4	selected
 3	I/O error
 2-1	unused
 0	timeout
Notes:	If both, bit 5 "out of paper" and 4 "selected" are set, the MS-DOS/
	  PC DOS kernel assumes that no printer is attached.
	for Tandy 2000, bit 7 indicates printer-busy when set rather than clear