Compiling and running the code

Once you finish writing your source code, the next step is always its compilation which generates the executable code. To compile your code, type the following line in your terminal:

   g77 fact.f -o fact.exe

This causes that g77 compiler reads the Fortran source code fort.f, searches for errors in this file, translates it to the machine language and produces the executable file fact.exe (on Mac, you are free to avoid the extension .exe). Although it should not be the case here, you can sometimes encounter warnings and/or error messages produced by the compiler. If it finds errors in your source code, it also tells you what is wrong. Your task is then to go back to Emacs, find the error and fix it. Remember, the executable code is not produced unless the compilation finishes without errors.

If you correctly typed the program above, the current directory should now contain the executable file fact.exe. Check this by typing dir (on Windows) or ls (on Mac). Your program can now be executed by writing fact (on Windows) or ./fact (on Mac) in your command-line terminal. The output of this program should look exactly as follows:

  Factorial of   5 is   120