title: PIC and XC8 Compiler issue
body: <p>Im sure Im missing something simple, and obvious, but I am tired of searching for the answer.  Im using a <code>PIC16F688</code> and <code>XC8</code> compiler.  </p>
  
  <p>The compiler user manual says that there is a <code>delay function __delay_ms()</code>.  It says that <code>_XTAL_FREQ</code> must be defined.  </p>
  
  <p>Here is my code, but it does not accept the command.  What is wrong?</p>
  
  <pre><code>#include &lt;stdio.h&gt;
  #include &lt;stdlib.h&gt;
  
  #define _XTAL_FREQ 20000000
  
  #include&lt;xc.h&gt;
  
      int main(int argc, char** argv) {
  
  
         _delay_ms(4);
  
      return (EXIT_SUCCESS);
  </code></pre>