**Abstract:**
This paper explains by a series of examples the use of the
notion of a Chemical Abstract Machine. This is a framework for
parallel computations which builds upon the chemical metaphor of
Banatre and Le Métayer. We first illustrate the CHAM style by
describing the operational semantics of process calculi constructs.
Then we apply our approach to the lambda-calculus, designing a
CHAM for the weak beta-reduction with sharing, and specializing
it into a CHAM for the call-by-need reduction strategy. Our
last example is the pi-calculus. We discuss the notions of
``asynchronous'' and ``fully asynchronous'' reductions, and some
pi-calculus encodings of the lambda-calculus.

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