Abstract: A programmable controller of the type used to solve relay ladder diagrams is taught. The programmable controller includes a memory into which is placed a digital representation of the rungs of the ladder diagram. The disposition of various switches and coils are periodically sampled by other portions of the programmable controller and stored in other memory locations. At appropriate times between sampling intervals, the various memory information are combined and provided to a relay line solver which comprises part of the programmable controller. The sequence in which the information is provided to the relay line solver is determined by the sequence of ladder diagram entry into the memory by the programmer. The sequence of entry is determined during the entry process in a real time frame by apparatus within the programming panel which utilizes the interconnection of contact information which is provided by the operator in the manipulation performed.