title: How to link two Fortran files
body: <p>I am very new to Fortran and want to ask how can I run a main program in one Fortran file from another Fortran file.</p>
  
  <p>For instance, I have two Fortran files: <code>a.for</code> and <code>b.for</code>, Inside <code>a.for</code>, there is a main program called <code>xx</code>:</p>
  
  <pre><code>program xx
  ....
  ....
  end program xx
  </code></pre>
  
  <p>Inside <code>b.for</code>, there is a main program called <code>yy</code>:</p>
  
  <pre><code>program yy
  ....
  (Call the main program xx from a.for)
  ....
  end program yy
  </code></pre>
  
  <p>Is it possible to do that?</p>