etags is an useful tool to generate tag tables for Emacs (ctags is the same but for vi). This allows us to jump to a function defined in some file in the code, without having to remember in which file is it. As could be expected, this tool understand the syntax of a lot of programming languages, like C, C++, Fortran, HTML or LaTeX.
To use it, in the folder where the code is run
etags *.f90
This generates a file called TAGS with the information (a tag table) about in which .f90 is each function and subroutine of the code.
Then, in Emacs move the cursor on the subroutine/function what you want, and ATL+. (ALT and dot) opens the .f90 file where the subroutine/function is with the cursor on the definition of it. To go back, hit ALT+, (ALT and comma).
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