title: Set a virtual function declaration to zero?
body: <blockquote>
    <p><strong>Possible Duplicate:</strong><br>
    <a href="https://stackoverflow.com/questions/2156634/why-pure-virtual-function-is-initialized-by-0">Why pure virtual function is initialized by 0?</a>  </p>
  </blockquote>
  
  
  
  <p>In C++, what does it mean to set a function declaration to zero?  I'm guessing it has to do with the function being virtual, and not actually defined in this class.  Found in a header file of code that I'm reading:</p>
  
  <pre><code>virtual void SetValue(double val)=0;
  </code></pre>
  
  <p>What's going on here?</p>