     unpka     headr
     * Convert the 3-character address in )0a, which is destroyed,   )0T
     * to a five-digit number in )02.                                )0T
     * Convert the 3-character address in index )0c, which is
     * destroyed, to a five-digit number in )02.                     )0C
     * A word mark is needed at )0a-2.                               )0T
     * A word mark is needed at )0c-2.
     * If both arguments )01 and )03 appear, )03 takes priority.  )0A)0C
     )00       mn   )0C,)02        Digits
     )00       mn   )01,)02        Digits                            )0T
               mn                    to  
               mn                      output
               b    )0k
     )0j       sbr  )0c,15000&)0C  Decrement address by 1k
     )0j       ma   @?0?@,)01      Decrement address by 1k           )0T
               a    @1000@,)02
     )0k       c    )02,)0c
     )0k       c    )02,)01                                          )0T
               bu   )0j
