+of type \texttt{std::Add}. If you type:
+\begin{verbatim}
+> help workspace
+\end{verbatim}
+
+You get information about the actual instance \texttt{a} of the box type \texttt{std::Add}. It gives something like this:
+\begin{verbatim}
+> help a
+ Black Box 'a' <std::Add>
+ * Inputs :
+ 'BoxExecute' = '? (no adaptor found)' [Modified]
+ 'BoxProcessMode' = 'Pipeline' [Modified]
+ 'In1' = '0' [Modified]
+ 'In2' = '0' [Modified]
+ * Outputs :
+ 'BoxChange' = '? (no adaptor found)' [Out-of-date]
+ 'Out' = '0' [Out-of-date]
+\end{verbatim}
+Note that the inputs appear as \texttt{[Modified]}, since the code defining the box type includes an initialization of the inputs. On the other hand, the outputs appear as \texttt{[Out-of-date]}, as the box has not yet been executed and therefore its outputs have not been updated. See the second part of this section to learn more about the updating. For a moment, just note that one way to process the box \texttt{a} is to use the command:
+\begin{verbatim}
+> exec a
+\end{verbatim}
+
+This command does not display anything (except if the
+box itself displays something in its processing).
+It just processes the box if needed. In our case, the result can be seen as follows:
+\begin{verbatim}
+> exec a
+> help a
+ Black Box 'a' <std::Add>
+ * Inputs :
+ 'BoxExecute' = '? (no adaptor found)' [Up-to-date]
+ 'BoxProcessMode' = 'Pipeline' [Up-to-date]
+ 'In1' = '0' [Up-to-date]
+ 'In2' = '0' [Up-to-date]
+ * Outputs :
+ 'BoxChange' = '? (no adaptor found)' [Up-to-date]
+ 'Out' = '0' [Up-to-date]
+\end{verbatim}
+Note the change of status of all the inputs and outputs (\texttt{[Up-to-date]}).
+In practice, the command \texttt{exec} is useful to execute boxes that do not have any output,
+such as boxes that write something to a file or, display a
+graphical interface, and so on.
+
+Now, let us set the input \texttt{In1}