Start the text editor program called pico by typing the command:
We use the .f extension to signify that we are writing a FORTRAN program and in fact the FORTRAN compiler requires a .f filename extension.
You will then see a screen as shown. This will be blank document which we can type the text of our FORTRAN program
To save, exit using crtl-X, save changes to buffer and then save file.
Then you'll wish to compile the program.