Abstract: A system for automatically determining the logical function of a circuit using a logic simulator wherein the input stimuli and truth table for a known or unknown circuit are determined directly from the input and output node data of the circuit without the user having to specify input transition values. The system of the invention automatically determines the truth table and input stimuli of the circuit by communicating with the logic simulator through a communications interface and applying every possible combination of input edges to the logic simulator to determine which input edges cause changes in the outputs. In particular, from a list of inputs and outputs of the circuit, the invention creates a complete set of binary vectors in input space and sends them to the logic simulator. It then examines the state of the output returned from the logic simulator in order to determine which input-to-output paths exist.