Determines whether the archive is storing data.
Nonzero if the archive is currently being used for storing; otherwise 0.
This member function is called by the Serialize functions of the archived classes.
If the IsStoring status of an archive is nonzero, then its IsLoading status is 0, and vice versa.
extern CArchive ar;
if( ar.IsStoring() )
ar << i;
ar >> i;