"FORTRAN IV/77 has some statements that IIRC correctly have or will be removed from the newer fortran" Right, importantly GOTO. The question I've puzzled over

"FORTRAN IV/77 has some statements that IIRC correctly have or will be removed from the newer fortran" Right, importantly GOTO. The question I've puzzled over for some while is how much legacy (unmodified) FORTRAN IV/77 applications/libraries still exist and are in regular use—and whether porting this old code to later Fortran or other languages remains a significant problem. My interest stems from the fact my first language was FORTRAN IV.