PROGRAM DCONCAT
      INTEGER A(15),B,END
      DATA END/'.E'/
   10 CONTINUE
      WRITE(6,100)
      READ(5,200)A
      CALL OPENF(2,A,IERR)
      IF(IERR.NE.1)GOTO 10
      WRITE(6,101)
      GOTO 20
   15 CONTINUE
      WRITE(6,102)
   20 CONTINUE
      READ(5,200)A
      IF(A(1).EQ.END)GOTO 50
      CALL OPENF(1,A,IERR)
      IF(IERR.NE.1)GOTO 20
   30 CONTINUE
      CALL RDSEQ(1,B,2,IERR)
      IF(IERR.NE.1)GOTO 40
      CALL WRSEQ(2,B,2)
      GOTO 30
   40 CONTINUE
      CALL CLOSF(1,IERR)
      GOTO 20
   50 CONTINUE
      CALL CLOSF(2,IERR)
      STOP
  100 FORMAT('  ENTER O/P FILENAME')
  101 FORMAT('  ENTER I/P FILENAME')
  102 FORMAT('  ILLEGAL FILENAME')
  200 FORMAT(15A2)
      END