It is as follows
........
16 FC=FB $ FB=F
DA=DB $ DB=D
GOTO 21
........
or on another place:
........
5 FC=FB $ FB=FA $ FA=F
DC=DB $ DB=DA $ DA=D
.......
The book where I am taking the code from is dated 1972 so it is written probably in an earlier version of FORTRAN. I noticed, that there might be two versions of FORTRAN, once the author uses in an IF clause ...IF(Y(I).EQ.1) GOTO 4 and somewhere else ..IF(Y(I)) 4,5,6, but it is not a problem. It is the dollar sign that I am not sure about. On internet I found an explanation that a $ sign prevents carriage return by printing but there is no print here in my case.
regards
Dixiematic