**Abstract:**

We introduce three notions of computation for processes described as
CCS terms. The first one uses an adaptation of the equivalence by
permutations of Berry and Lévy. In this setting, a computation
is an equivalence class of sequences of transitions, up to the
permutation of independent steps. The second notion of computation is
given by means of an interpreataion of CCS into a new class of event
structures, the flow event structures. This can be seen as a
reformulation of Winskel's semantics for CCS by means of stable event
structures. Here a computation is a configuration of an event
structure. Finally, our third notion of computation is determined by
an interpretation of CCS terms as Petri Nets, and more precisely as
flow nets. Here a computation is a set of events firable in sequence
in the net. We then show that these three computation interpretations
of CCS coincide, in the sense that for a given term, the three
domains of computations are isomorphic. To this end we use an
intermediary transition system for CCS, where the past is recorded;
this appears to be a system of ``trace computations'', which provides
another means to define the same abstract domain of computations.