title: Unsigned Binary Subtraction ( 0011 - 1111 = 0100 ?)
body: <p>I'm currently building a 4-bit bitwise adder-subtractor for a project at university but the subtraction doesn't all make sense to me. I have it working for positive values <code>1100 - 0100 = 1000</code> but I'm not sure that my answer is correct when the result is negative. As can be seen in the title, when I do <code>0011 - 1111</code> for unsigned subtraction my result is <code>0100</code>. Could someone verify to me that this is the correct answer and that neither the overflow or carry should be <code>1</code> when this calculation is carried out?</p>