title: cli before start in bootloader
body: <p>I found 512 byte os contest during web surfing.</p>
  
  <p>everything is fitted in bootsector.</p>
  
  <p>after read some of those source files,</p>
  
  <p>I found there is always <code>cli</code> instruction before start routine.
  (in assembly)</p>
  
  <pre><code>use16
  org 7c00h
  jmp 0:start
  start:
    cli
    do something here..(this section sometimes include int 10h)
  </code></pre>
  
  <p>the thing I wonder is </p>
  
  <ol>
  <li><p>why <code>cli</code> is necessary before start routine.</p></li>
  <li><p>after <code>cli</code>, sometimes, they use interrupt! like <code>int 10h</code> I wonder why they use interrupt after <code>cli</code> would it be normal?</p></li>
  </ol>