The reengineering of digital circuits is becoming an increasingly important problem in design automation, as the number of existing systems grow. To effectively redesign a digital system, it must be completely described at a level detailed enough to allow for the synthesis of a new design. Frequently, the original specifications are outdated or unavailable, so it is necessary to recover the design directly from the hardware component. Recovering this level of design from an existing implementation may be complicated as a result of errors in the original design, incomplete information or missing documentation. Determination of functional roles of the system components is the starting point of reengineering. This lecture presents an algorithm that helps in faster identification of functional roles of a system component. Existing techniques make use of the semantic matching approach, which significantly reduce the number of correspondences between the unknown and the model library circuit. This algorithm is an improved version of the semantic matching approach. The technique specified in the algorithm reduces the number of correspondences between the functional inputs of unknown circuit and a model library circuit, thus reducing the number of equivalence checks necessary. This lecture talks about the software implementation of the algorithm and its corresponding results in comparison with earlier techniques. This algorithm provides a mechanism for faster recovery of combinational device designs and for the combinational logic present in sequential devices.