title: Subtracting a large unsigned binary number from a smaller one
body: <p>I'm taking a computer organization and assembly language course.  The written part of our lab this week has a question on it that has me stumped.  The question reads...</p>
  
  <p><strong>Subtract the following unsigned binary numbers (show the borrow and overflow bits).  Do not convert to two's complement.</strong></p>
  
  <pre><code> 0101 0111 1101
  -1110 1011 0110
   --------------
  </code></pre>
  
  <p>I realize that the answer is <strong>-1001 0011 1001</strong> but I'm having a hard time trying to figure out how to borrow to actually perform this subtraction by taking the larger number and subtracting it from the smaller number and show my work.  My whole life when subtracting a large number from a small number I have reversed the problem and instead subtracted the smaller number from the larger number and added a negative sign in front of the result.  I asked the professor and he says that he wants the problem solved the way that it is written.  I am not allowed to solve this by subtracting the smaller number from the larger number and negating like I normally would.  I haven't been able to find any examples online of subtracting a larger unsigned binary number from a smaller one.</p>
  
  <p>I would really appreciate it if someone could describe to me how to perform subtraction in this scenario.</p>
  
  <p>Update:
  @Alex is correct.  The professor was looking for</p>
  
  <pre><code>0110 1100 0111 (1735)
  </code></pre>
  
  <p>Thanks everyone.</p>