Regarding Oracle External procedure

Hi,

Can anyone shed some light of the below procedure?

I do not have much idea on external procedures.

create or replace PROCEDURE XXPQ_BARCODE (p_track     IN     CHAR,

                                          route       IN     CHAR,

                                          v_barcode      OUT CHAR)

AS

   EXTERNAL

   NAME "encodetr"

   LIBRARY sys.usps4cb_lib

   LANGUAGE C

   PARAMETERS (p_track String, route String, v_barcode string);

Thanks,

Krishna