F file extension is used by Fortran programming language. F is a text file containing Fortran code, and can be viewed using and text editor. Developers, however, used dedicated IDEs (Integrated Development Environment) such as Photran, which offer various quality-of-life features, for example, syntax highlighting, autofill function, etc.

Code stored in F file is first processed by preprocessor that runs before a compiler and generates output code. Next, the code is passed to compiler, which generated the actual machine code.