Testing of logic networks by verifying the Walsh coefricients of the outputs is explored. Measurement of one of these can detect arbitrarily many input leads stuck, and just two measurements, requiring little hardware, can detect any single stuck-at fault in appropriately designed networks.

A compatibility relationship on network paths is defined in such a way that the maximal compatibles are isomorphic to the products in the "structure and parity-observing output function" (SPOOF), a subscripted Boolean expression for the network output that uniquely specifies the network structure. For a given network, the path compatibility relations are easy to find, as are the maximal compatibles and hence the SPOOF for the network output. Because the collection of all the path compatibility relations, conveniently displayed in matrix form, completely characterizes the network, the compatibility matrix can be used for a variety of purposes.

In this correspondence it is shown that by applying Gavrilov's test algorithm to any Boolean function numerically represented by its "constrained designation numbers", introduced by Ledley, a very suitable program for the automatic determination of the prime implicants and of the prime implicant table can be established.

Flexibility, accuracy, elimination of manual skill, and greater work potential result from the addition of digital data processing to machine-tool control. Several special-purpose digital computers for machine-tool control have now been developed. These perform only simple computational tasks. The more sophisticated tasks require the addition of general-purpose large-scale computers. This combination, while only partially explored, appears very promising. It should lead not only to improvements in translating a part design into the finished piece, but should ultimately assist in the design procedure.