The RWxmsg class serves as a base class for the various exception types that can be thrown and caught within the Essential Tools Module library, or from within Essential Tools Module client applications.

The Essential Tools Module uses the following hierarchy.

As shown in Figure 9, RWxmsg serves as a base class for all exception types. From this point, the three major types of exceptions are derived: external errors, internal errors, and stream buffer allocation errors. Let us describe each of these classes in greater detail.