Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Link List
GV_LINK_LISTParameter: Index
GV_LINK_OPERATOR_INDEXParameter: Link
GV_LINK_OUTPUTParameter: Count
GV_LINK_OUTPUT_COUNT