Editing Communicating sequential processes (section)

=== Syntax ===
{{unreferenced section|date=November 2024}}

The syntax of CSP defines the “legal” ways in which processes and events may be combined. Let {{mvar|e}} be an event, and {{mvar|X}} be a set of events. Then the basic [[syntax]] of CSP can be defined as:

<math display="block">
\begin{array}{lcll}
{Proc} & ::= & \mathrm{STOP} & \; \\
&|& \mathrm{SKIP} & \; \\
&|& e \rightarrow {Proc} & (\text{prefixing})\\
&|& {Proc} \;\Box\; {Proc} & (\text{external} \; \text{choice})\\
&|& {Proc} \;\sqcap\; {Proc} & (\text{nondeterministic} \; \text{choice})\\
&|& {Proc} \;\vert\vert\vert\; {Proc} & (\text{interleaving}) \\
&|& {Proc} \;|[ \{ X \} ]| \;{Proc} & (\text{interface} \; \text{parallel})\\
&|& {Proc} \setminus X & (\text{hiding})\\
&|& {Proc} ; {Proc} & (\text{sequential} \; \text{composition})\\
&|& \mathrm{if} \; b \; \mathrm{then} \; {Proc}\; \mathrm{else}\; Proc & (\text{boolean} \; \text{conditional})\\
&|& {Proc} \;\triangleright\; {Proc} & (\text{timeout})\\
&|& {Proc} \;\triangle\; {Proc} & (\text{interrupt})
\end{array}
</math>

Note that, in the interests of brevity, the syntax presented above omits the <math>\mathbf{div}</math> process, which represents [[Divergence (computer science)|divergence]], as well as various operators such as alphabetized parallel, piping, and indexed choices.