-In a similar way, one can obtain the information about any box from the loaded packages, by executing the command \texttt{help} \emph{box\_name}. Note that some boxes may be unavailable if the command \texttt{load} was used to load the package, since this command only loads the boxes in binary. Some boxes are defined in script files. To be sure that all the boxes from the package are loaded the command \texttt{include} is to be preferred.\par
-You can also get the list of the objects currently present in the workspace, by executing the command \texttt{help workspace}.
+In a similar way, one can obtain the information about any box from the loaded packages, by executing the command \texttt{help} \emph{box\_name}. Note that some boxes may be unavailable if the command \texttt{load} was used to load the package, since this command only loads the boxes defined in binary files (dynamic libraries). Some boxes are defined in script files. To be sure that all the boxes from the package are loaded the command \texttt{include} is to be preferred.\par
+
+It is important to note that the black boxes are implemented and have to be used according to the {\bf\emph{object-oriented}} programming principles. This means that you have to make difference between a black box {\bf\emph{type}} and an {\bf\emph{instance}} of the given black box type. The former defines a ``pattern'' (a mold), according to which are formed the actual objects. If you query for help on a black box type, you learn about its purpose, its author, the boxes it contains (if it is a complex black box) and the types of its inputs/outputs. The user-defined black box types belong to the package \texttt{user} and can be listed by use of the command \texttt{help user}. If you query for help on a black box instance, you learn about the values and the state of its inputs/outputs. The currently existing black box instances belong to the complex black box \texttt{workspace} and can be listed by use of the command \texttt{help workspace}.