SUBROUTINE DATFIL(LUN,FNAME,L)
	DIMENSION FNAME(L)
	BYTE FNAME,Q
 1	Q=.FALSE.
	CALL INSTRI(FNAME,L-1,Q,'DATA FILE: ')
	IF(Q) GOTO 9
	LL=LEN(FNAME)
	IF(LL.EQ.0) CALL EXIT
	I=INDEX(FNAME,'.')
	IF(I.NE.0) GOTO 100
	CALL CONCAT(FNAME,'.DAT',FNAME,L-1,Q)
	IF(Q) GOTO 9
	LL=LL+4
 100	L=LL
	IF(LUN.GT.0) OPEN(UNIT=LUN,NAME=FNAME,TYPE='OLD',READONLY,ERR=1)
	RETURN
 9	TYPE *,'ERROR IN DATFIL -- NAME TOO LONG'
	GOTO 1
	END