All INT 17H services return the printer port status as a set of bit flags
in AH as follows:

PrinterStatusRec
 7 6 5 4 3 2 1 0 
           0 0   
           - -    bit  mask
                  0: 01H  1 = time-out error
                  3: 08H  1 = I/O error
                  4: 10H  1 = selected (0 means off-line)
                  5: 20H  1 = out of paper
                  6: 40H  1 = acknowledge (printer is attached)
                  7: 80H  1 = not busy (note: 0 means busy)

INT 17H (BIOS printer support)
- -

BIOS Printer Status Flags