title: C++ header file and function declaration ending in "= 0"
body: <p>I have the following code inside the .h file and I'm not sure what does the assignment statement do and how is it called properly?</p>
  
  <pre><code>virtual void yield() = 0;
  </code></pre>
  
  <p>I thought that the function returns a value of 0 by default but since this function returns void I am a little bit confused. Can anyone comment on this and maybe say how can I refer to this assignment, I mean how is it called in C++ jargon?</p>
  
  <p>Thanks.</p>