SUBROUTINE FIELD( IN, NCHRS, NAT )
C
C	This subroutine advances the pointer NAT in the character
C	string IN past the next occurence of either a <SP>, <TAB>
C	or comma.  If none is found, the pointer is set to the
C	length of the string plus one (NCHRS+1).
C
	LOGICAL*1 IN(1)
C
C - TRY AND FIND A DELIMITER.
100	CALL ITWAS( IN(NAT), ' 	,', 3, ITIS )
	NAT = NAT+1
	IF( ( ITIS .LE. 3 ) .OR. ( NAT .GT. NCHRS ) ) RETURN
	GO TO 100
	END