  We consider both channel coding and source coding, with perfect past
feedback/feedforward, in the presence of side information. It is first observed
that feedback does not increase the capacity of the Gel'fand-Pinsker channel,
nor does feedforward improve the achievable rate-distortion performance in the
Wyner-Ziv problem. We then focus on the Gaussian case showing that, as in the
absence of side information, feedback/feedforward allows to efficiently attain
the respective performance limits. In particular, we derive schemes via
variations on that of Schalkwijk and Kailath. These variants, which are as
simple as their origins and require no binning, are shown to achieve,
respectively, the capacity of Costa's channel, and the Wyner-Ziv rate
distortion function. Finally, we consider the finite-alphabet setting and
derive schemes for both the channel and the source coding problems that attain
the fundamental limits, using variations on schemes of Ahlswede and Ooi and
Wornell, and of Martinian and Wornell, respectively.
