Here are the data structures with brief descriptions:

C_timeb	Used by ftime. Defined as _timeb (instead of timeb) just as in the on-line Help
Clconv	Returned by localeconv. Documented at http://www.cplusplus.com/reference/clocale/lconv/
Ctm	Documented at http://www.cplusplus.com/reference/ctime/tm/. Values outside of valid ranges can be used to calculate a new date/time using mktime. E.g. tm_mday = 0 means last day of previous month
Cy_browser	Internal browser structure, describing a browser as an entity
Cy_flow	Descriptor for one single flow in a flow list