1. A programmable fast comparison unit for use in apparatus providing a fast comparison between a specified binary number and a result binary number, said result binary number resulting from a binary operation involving two operands, said fast comparison unit comprising: control signals for indicating a selection of the specified binary number; a plurality of compare units, each compare unit receiving an n.sup.th and (n-1).sup.th bits of each operand, said each compare unit responsive to said control signals for providing a predetermined signal when an n.sup.th bit of said result binary number is the same as a selectable n.sup.th bit of said specified binary number and conditional on an (n-1).sup.th bit of said result binary number being equal to a selectable (n-1).sup.th bit of said specified binary number.