With the printing initiation instruction, {HEAD ~ the printer} and {TAIL ~ the host computer} perform the two way communication through the parallel communication I/O interfaces 
With the printing initiation instruction , { HEAD ~ the printer } and { TAIL ~ the host computer } perform the two way communication through the parallel communication I / O interfaces
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH