title: Where does the k prefix for constants come from?
body: <p>it's a pretty common practice that constants are prefixed with <code>k</code> (e.g. <code>k_pi</code>). But what does the <code>k</code> mean?</p>
  
  <p>Is it simply that <code>c</code> already meant <code>char</code>?</p>