1. A method of classifying an input pattern into an associated output class, comprising: determining, for each of a plurality of classification rungs, each representing at least one output class, the a priori probability that an input pattern will be associated with a class represented by that rung; assigning a sequential order of processing for the plurality of classification rungs based upon the a priori probability associated with each classification rung; computing a confidence value associated with a represented class for each classification rung, in the assigned order, until a class is selected or a termination event occurs; comparing the associated confidence values to a predetermined threshold; and selecting a class associated with a confidence value that first exceeds the threshold, if a confidence value exceeds the threshold.