Although there are no official file extensions for Fortran CODE, there are two widely established conventions. Some use .f for fixed-form source and .f90 for Free form LAYOUT. The latter is a reference to the Fortran 90standard, when Free form layout was introduced. The code contained in the file can be Fortran 95, Fortran 2003, etc. Others prefer to use file extensions that indicate the standard under which the code was written. For EXAMPLE, .f03 for Fortran 2003 code and .f08 for Fortran 2008 code. Unfortunately, this RESULTS in a proliferation of file extensions and some compilers may not support the newer extensions yet.

Although there are no official file extensions for Fortran code, there are two widely established conventions. Some use .f for fixed-form source and .f90 for Free form layout. The latter is a reference to the Fortran 90standard, when Free form layout was introduced. The code contained in the file can be Fortran 95, Fortran 2003, etc. Others prefer to use file extensions that indicate the standard under which the code was written. For example, .f03 for Fortran 2003 code and .f08 for Fortran 2008 code. Unfortunately, this results in a proliferation of file extensions and some compilers may not support the newer extensions yet.