AbstractCahn–Ingold–Prelog (CIP) rules 1 and 2 (material differences) have been expressed in the formal logic of a high‐level computer language (FORTRAN IV) on a laboratory minicomputer (PDP 11/40) by the program CHIRAL. An oversight in the CIP formalism in the treatment of rings was treated on anad hocbasis; the problem has been expressed simply in terms of elementary graph theory in a way consistent with and similar to chemical notation. An example of the operation of CHIRAL is provided and the internal procedu