Events triggered by the XceedZip object are communicated either by callback or by a window message. In both cases, an event index number is provided, along with a data structure containing the event's parameters. The event index number is a unique number that lets you identify which event occurred and what parameters are contained in the provided data structure.
Events that have strings in their parameters are available in both ANSI and Wide-character versions. If you got your handle to an XceedZip with the ANSI version of XzCreateXceedZip, then all reported strings will be ANSI strings (char *). But if you called the UNICODE version of XzCreateXceedZip, then all reported strings are UNICODE strings (WCHAR *).
In each event topic, you will see the generic parameter structure, using the TCHAR data type, which is mapped to char or WCHAR, depending on your compiler settings.
Below is a table of event indexes, and the available defines in XceedZipAPI.h: