  There is one, and only one way, consistent with fundamental physics, that the
efficiency of general digital computation can continue increasing indefinitely,
and that is to apply the principles of reversible computing. We need to begin
intensive development work on this technology soon if we want to maintain
advances in computing and the attendant economic growth.
  NOTE: This paper is an extended author's preprint of the feature article
titled "Throwing Computing Into Reverse" (print) or "The Future of Computing
Depends on Making it Reversible" (online), published by IEEE Spectrum in
Aug.-Sep. 2017. This preprint is based on the original draft manuscript that
the author submitted to Spectrum, prior to IEEE edits and feedback from
external readers.
