Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Ring Radius
PRIM_TORUS_OUTERRADParameter: Ring Segments
PRIM_TORUS_SEGParameter: Pipe Radius
PRIM_TORUS_INNERRADParameter: Pipe Segments
PRIM_TORUS_CSUBParameter: Switch to Updated Torus
PRIM_TORUS_SWITCH_TO_UPDATED