1. A neural network alphanumeric pattern recognition machine comprising: means for receiving indicia of known and unknown alphanumeric symbols; a data base for storing received indicia of the known alphanumeric symbols and classifying each of said alphanumeric symbols according to a known class of an alphanumeric symbol, thereby to assign an alphanumeric class to each known alphanumeric symbol; an alphanumeric pattern classifier connected to said data base for determining alphanumeric classes of unknown symbols represented by input signals to said machine; means for training said classifier to perform a recognition function in a manner that is invariant with respect to small transformations of each said known alphanumeric symbol, said means for training comprising: means for expressing each said known alphanumeric symbol as a vector quantity; means for computing one or more tangent vectors from each said vector quantity, each said tangent vector being an indicia of a particular small transformation of said known symbol; means for combining said one or more tangent vectors, thereby to derive a combined value representative of an additional alphanumeric symbol which by definition is a member of the alphanumeric class of the known alphanumeric symbol from which derived; and means for augmenting said data base with said additional alphanumeric symbols.