  Recently we introduced a class of number representations denoted
RN-representations, allowing an un-biased rounding-to-nearest to take place by
a simple truncation. In this paper we briefly review the binary fixed-point
representation in an encoding which is essentially an ordinary 2's complement
representation with an appended round-bit. Not only is this rounding a constant
time operation, so is also sign inversion, both of which are at best log-time
operations on ordinary 2's complement representations. Addition, multiplication
and division is defined in such a way that rounding information can be carried
along in a meaningful way, at minimal cost. Based on the fixed-point encoding
we here define a floating point representation, and describe to some detail a
possible implementation of a floating point arithmetic unit employing this
representation, including also the directed roundings.
