GNU Fortran

GNU Fortran or GFortran is the GNU Fortran compiler, which is part of the GNU Compiler Collection (GCC).
It includes full support for the Fortran 95 language, and supports large parts of the Fortran 2003 and Fortran 2008 standards. It supports the OpenMP multi-platform shared memory multiprocessing, up to its latest version (4.5). GFortran is also compatible with most language extensions and compilation options supported by g77, and many other popular extensions of the Fortran language.
Since GCC version 4.0.0, released in April 2005, GFortran has replaced the older g77 compiler. The new Fortran front-end for GCC was rewritten from scratch, after the principal author and maintainer of g77, Craig Burley, decided in 2001 to stop working on the g77 front end. GFortran forked off from g95 in January 2003, which itself started in early 2000. The two codebases have "significantly diverged" according to GCC developers. Since 2010 the front-end, like the rest of the GCC project, has been migrated to C++, where it was previously written in C.