We present an algebra that is intended to bridge the gap between programming formalisms that have a high level of abstraction and the operational interpretations these formalisms have been designed to capture. In order to piece a high-level formalism sound for its intended operational interpretation, one needs a mathematical handle on the latter. To this end we design the computation calculus. As an expression mechanism, it is sufficiently transparent to avoid begging the question. As an algebra, it is quite powerful and relatively simple. (C) 2000 Published by Elsevier Science B.V. All rights reserved.