title: 2's complement binary multiplication
body: <p>I am a little confuse with how do we perform signed 2's complement multiplication.</p>
  
  <pre><code>         10 1101        -19
         x 11 0001     x  -15
        ----------------  ------
            101101         285
           000000
          000000
         000000
        101101
       101101
      ----------------
     100010011101
  </code></pre>
  
  <p>Adding all the calculations I get "100010011101" as stated which is not 285 signed, why?</p>