title: `os.system` yields a multiple of 256?
body: <p>In python2, I have the following</p>
  
  <pre><code>&gt;&gt;&gt; os.system('exit 1')
  256
  &gt;&gt;&gt; os.system('python -c "import sys; sys.exit(125)"')    
  32000
  </code></pre>
  
  <p>Why are these multiples of 256?</p>