Virtually all compilers still support them, even the most modern compilers that support Fortran 2018 (Intel, GNU, IBM, NAG, ...). The source file extensions rea

Virtually all compilers still support them, even the most modern compilers that support Fortran 2018 (Intel, GNU, IBM, NAG, ...). The source file extensions readily tell the compiler what sort of code the compiler is dealing with. In the worst case scenarios that I have seen, the compiler issues a warning when encountering obsolescent language features.