egister labelled SR contains four flag bits that give information 
  about the state of the CPU. There are three flags that indicate whether a calculation 
  overflowed, gave a negative result or gave a zero result. Calculations set these 
  flags </p>
<ul>
  <li>S The sign flag indicates a negative result.</li>
  <li>O The overflow flag indicates overflows.</li>
  <li>Z The zero flag indicates a zero result.</li>
  <li>I Interrupts enabled. STI turns this on. CLI turns this off.</li>
</ul>
<p>The