A miniaturized computer controller system utilizes reprogrammable "read only" ultraviolet memory chips instead of conventional core memories to store a control program comprising variable information regarding all electrical elements in all electrical circuit lines of the controller. The memory chips are reprogrammable within the controller and thus delicate removal of the chips for reprogramming is eliminated. The controller utilizes a central processor removably interfitting with a reprogramming module that also communicates with a programming panel.When in a "monitor" mode, the programming panel, in conjunction with the reprogramming module, allows the operator to view any particular electrical circuit line while the controller is operating. A scroll switch on the programming panel further allows the operator to view sequentially higher or lower numbered electrical circuit lines while a trace switch provides for examining any electrical circuit line to which a currently viewed element is referenced.When in a " program" mode, the programming panel, in combination with the reprogramming module, replaces the variable memory "read only" chips and allows the controller to continue operation while the operator is programming, adjusting, or de-bugging the electrical circuit lines. Following the programming of the electrical circuit lines with the desired electrical elements, the information regarding these lines is transferred to the reprogrammable "read only" memory chips when the programming panel is in a "write" mode. In this mode all the information previously stored in the memory chips is first erased by ultraviolet light, followed by the insertion of the new information regarding the electrical circuit lines.Following the transferral of information to the memory chips, the reprogramming module is disconnected from the central processor and replaced by a removably interfitting power supply module, whereby the system operates with electrical circuit line information stored in the reprogrammable memory chips.