title: 2's complement minimum bits of a given number
body: <p>I'm trying to figure it out but still stuck. </p>
  
  <p>Let's say we have the decimal number <strong>13 (1101 in binary)</strong>. At unsigned, we need minimum 4 bits to represent it (1101 as it is) but in 2's complement signed do we need 5 bits with the MSbit set to 0 because 13 is a positive number? I know that in 2's complement, the MSbit indicates the sign of the value (+ or -). So it will be 01101?
  Also, if the MSbit is 0, the number is still the same in singed 2's complement but if it is 1 then is will be As = Au - 2^n.</p>
  
  <p>Let's say now that the number is <strong>-13</strong>. To find out the binary form of -13, i flip all the bits of 13 (1's complement) and then add +1 to them (2's complement). So in this case we have: <code>1101 ---&gt; 0010 + 1 ---&gt; 0011</code> but in singed 2's complement the MSbit is 0 (so it's positive) and we say "<strong>this is the number 3</strong>" or can we 1 as the new MSbit to look like negative (like 11101)?</p>
  
  <p>Thanks :)</p>