This is possible if you do it in the following way, that is if you use the new continuation sign "&" at the end of the old line, but in position 73 so that it doesn't conflict with Fortran 77, and also choose the "&" sign as the almost arbitrary character in column 6, in order to get continuation according to Fortran 77. ... Comments are an incompatibility problem between Fortran 77 and Fortran 90, but of course not between fixed and free forms of Fortran 90 since the "!" is permitted in both. ...