1. A signal processor comprising: a crossbar array including one or more materials or molecular components formed between intersections of the crossbar array wherein the one or more materials or molecular components is programmable so as to have a corresponding programmed impedance value Zij at each of the intersections, where i is an integer ranging from 1 to N, j is an integer ranging from 1 to M, N corresponds to a number of input wires in the crossbar array, M corresponds to a number of output wires in the crossbar array at least one of N or M≧2 and the other one of N or M≧1; an input unit providing a set of N input signals Vin(i) directed toward the input wires of the crossbar array; and an output unit outputting a set of M output signals Vout(j) derived from the output wires of the crossbar array, wherein the crossbar array, input unit, and output unit are constructed so that each of the programmed impedance values Zij uniquely determines a corresponding value Tij such that 
 Vout( j )=Σ Tij ×Vin( i ), which is a summation performed for 1 ≦i≦N.