FUNCTION IRDBLK( LIST ,WORD ,DEBUG )
C+
C	FUNCTION IRDBLK WILL RETURN THE BLOCK NUMBER TO READ GIVEN THE
C	LETTER INDEX READ FROM THE DISK FILE.
C 
C	ONLY 102 LISTINGS ARE POSSIBLE (102*(5 LETTERS)) <512
C 
C	LOCAL VARIABLES
C		BFRAG	- THE FIRST 5 BYTES OF LIST ELEMENTS
C		CFRAG	- THE CHARACTER EQUIVALENT OF BYTE ARRAYC
C 
C	SUBROUTINES REFERENCED
C		CLEAR	- STORE NULLS IN THE ARRAY
C 
C-
	BYTE LIST(5,102)
	CHARACTER*25 WORD
	CHARACTER*5 CFRAG
	BYTE BFRAG(5)
	LOGICAL*1 DEBUG
	EQUIVALENCE (CFRAG,BFRAG(1))
C 
	DO 30,I=2,102					!CHECK ALL THE POSITIONS
	IF(LIST(1,I).EQ.'0'O)GO TO 40			!NULL ENDS LIST
	CALL CLEAR(BFRAG,5)				!CLEAR CHECK WORD
	DO 10,J=1,5					!FILL THE CHECK WORD
	IF(LIST(J,I).EQ.'0'O)GO TO 20			!NULLS AT END OF SHORT
10	BFRAG(J)=LIST(J,I)				!
20	CONTINUE					!
	IF(DEBUG)WRITE(3,1000)CFRAG
	IF(LLT(WORD(1:5),CFRAG))THEN			!HAVE GONE TOO FAR?
		IRDBLK=I-1				!YES, USE LAST
		GO TO 50				!THAT IS WHAT WE WANT
	END IF
30	CONTINUE
40	IRDBLK=I-1					!GONE TOO FAR, LAST ONE
50	IF(DEBUG)WRITE(3,1010)IRDBLK
	RETURN
1000	FORMAT(' CFRAG=',A5)
1010	FORMAT(' IRDBLK=',I4)
	END