__fastcall virtual TDBISAMDataSet(System::Classes::TComponent*
      AOwner)

Use the New operator to create an instance of a TDBISAMDataSet component using the constructor. However, you should not use this constructor to create an instance of this component directly. Instead you should create an instance of a TDBISAMTable or TDBISAMQuery component, which both descend from this component and provide a published interface for use at design-time.