Constructs a CArchive object and specifies whether it will be used for loading or storing objects.
You cannot change this specification after you have created the archive.
You may not use CFile operations to alter the state of the file until you have closed the archive. Any such operation will damage the integrity of the archive. You may access the position of the file pointer at any time during serialization by obtaining the archive's file object from the GetFile member function and then using the CFile::GetPosition function. You should call CArchive::Flush before obtaining the position of the file pointer.