extremely low value and therefore unable to interfere with ongoing communications between a printer controller 3 and a computer controller unit 1 due to the aforesaid high resistance i o pin characteristics the invention herein can be interfaced with more than 25 computers without the occurrence of operational errors but in a typical installation only about 15 computers are interfaced in addition the invention herein can executed by computer software and the aforesaid software is resident and capable of being initiated whenever any other software whatsoever is operating on the computer when the aforementioned resident software is initiated a small window listing the printer selection is displayed and the operator can select the number of the printer connected to port lpt1 and lpt2 at address 378h 278h or 3bch then input the data representing the choice to the controller ic of the computer controller unit and the controller ic of file printer controller unit the process of which occurs according to the following sequence of events when no printer is connected to the controller ic of the computer controller unit then the aforesaid controller ic scans the data output to determine whether or not a printer request is set if a printer request has been set then the controller ic of the computer controller unit will access the data output i o pin set for the selected printer and activate the aforesaid printer.