Editing Communicating sequential processes (section)

=== Original version ===
The version of CSP presented in Hoare's original 1978 article was essentially a concurrent programming language rather than a [[process calculus]]. It had a substantially different [[syntax]] than later versions of CSP, did not possess mathematically defined semantics,<ref name="hoare">{{cite book |last=Hoare |first=C. A. R. |author-link=C. A. R. Hoare |title=Communicating Sequential Processes |publisher=Prentice Hall |isbn=978-0-13-153289-2 |date=1985}}</ref> and was unable to represent [[unbounded nondeterminism]].<ref name="clinger1981">{{Cite thesis |first=William |last=Clinger |author-link=William Clinger (computer scientist) |title=Foundations of Actor Semantics |publisher=MIT |type=Mathematics Doctoral Dissertation |date=June 1981 |hdl=1721.1/6935}}</ref> Programs in the original CSP were written as a parallel composition of a fixed number of sequential processes communicating with each other strictly through synchronous message-passing. In contrast to later versions of CSP, each process was assigned an explicit name, and the source or destination of a message was defined by specifying the name of the intended sending or receiving process. For example, the process

 COPY = *[c:character; west?c → east!c]

repeatedly receives a character from the process named <code>west</code> and sends that character to process named <code>east</code>. The parallel composition

 [west::DISASSEMBLE || X::COPY || east::ASSEMBLE]

assigns the names <code>west</code> to the <code>DISASSEMBLE</code> process, <code>X</code> to the <code>COPY</code> process, and <code>east</code> to the <code>ASSEMBLE</code> process, and executes these three processes concurrently.<ref name="hoare1978" />