Intel® Fortran Compiler - effect of file extensions on source form The Intel® Fortran Compiler assumes that files with an extension of .f90 are free-form source files and that files with a .f, .for, or .ftn are fixed-form source. Linux* Apple Mac OS X* Microsoft Windows* (XP, Vista, 7) Fortran Intel® Fortran Compiler Intel Fortran Compiler extension free-form fixed-form Read more about Intel® Fortran Compiler - effect of file extensions on source form1 commentLog in to post comments