     The caret, or hat, character, '^', is used to distinguish 
            the exponent.

            The plus sign, '+', and the minus sign, '-' have the expected 
            meanings.

            In order to obtain the entire character string produced
            by this routine, the output character string should be
            at least N characters long, where


                      # of bits per double precision mantissa + 3
            N = 3 + ----------------------------------------------
       