PROGRAM chainwh

c	Changes alphabetic chain labels to numbers

	CHARACTER*65	line1, line2

	WRITE (6, 1000) 'Enter input filename:'
1000	FORMAT (a)
	READ (5, 1000) line1
	WRITE (6, 1000) 'Enter output filename:'
	READ (5, 1000) line2

	OPEN (unit=1, form='FORMATTED', status='OLD', readonly,
	1	file=line1)
	OPEN (unit=2, form='FORMATTED', status='UNKNOWN', file=line2,
	1	carriagecontrol='LIST')

c	Main loop

	DO WHILE (.TRUE.)
	  READ (1, 1000, end=9) line1
	  READ (line1(2:2), 1001) i
1001	  FORMAT (i1)
	  IF (line1(1:1) .EQ. 'A') THEN
	    i = 2*i-1
	  ELSE IF (line1(1:1) .EQ. 'B') THEN
	    i = 2*i
	  ELSE
	    WRITE (6, 1000) 'Illegal chain number'
	    WRITE (6, 1000) line1
	    GOTO 9
	  endIF
	  WRITE (line1(1:2), 1002) i
1002	  FORMAT (i2)
	  WRITE (2, 1000) line1
	endDO

9 	CLOSE (unit=1)
	CLOSE (unit=2)

	end