title: Are FORTRAN 77 programs faster than Fortran 90 ones?
body: <p>Today I was reading code from some very popular numerical libraries written in FORTRAN 77 such as QUADPACK (<a href="http://www.netlib.org/quadpack/changes" rel="nofollow">last updated in 1987</a>), and I was wondering if there is any reason not to rewrite those libraries in Fortran 90 apart from the big amount of work it would pose, given the great improvements Fortran 90 brought to the language, including free-form source, better control structures so GO TO could be forgotten, vectorization, interfaces and so on.</p>
  
  <p>Is it because FORTRAN 77 compilers produce more optimized code, maybe it is better for parallel execution? Notice that I'm not even talking about Fortran 2003 for example, which is <em>only</em> 8 years old: I'm talking about Fortran 90, so I assume it has enough widespread and the compilers are ready. I don't have contact with the industry, anyway.</p>
  
  <p>Edit: janneb is right: LAPACK is actually written in Fortran 90.</p>