Apparatus which discourages the use of unauthorized program software with proprietory computer hardware. The computer hardware reads a DATA TABLE from a specified location in separable software and displays the content of that table in human recognizable form. The displayed data is then compared with reference data which is stored in the proprietory hardware. The hardware blocks further execution of programs contained in the separable software if the displayed data and reference data are not congruent. In a preferred embodiment the display is material which can only be legally used with the permission of the manufacturer or proprietory of the hardware; for example; a registered trademark or copyrighted material.