title: Is it possible to use 32 bits registers/instructions in real mode?
body: <p>I'm confused about a simple assembly problem when studying some simple os source code.</p>
  
  <p>In this website: <a href="http://wiki.osdev.org/Babystep7" rel="noreferrer">http://wiki.osdev.org/Babystep7</a> the following code is to switch from real mode to protected mode</p>
  
  <pre><code>mov  eax, cr0
  or al,1
  mov  cr0, eax
  </code></pre>
  
  <p>I know how to switch from real mode to protected mode.<br>
  But my question is since the program is still in the real mode, how can it use the 32 bit registers or instructions?</p>
  
  <p>Is it possible to use 32 bits registers/instructions in real mode?</p>