title: Why is the Carry Flag set during a subtraction when zero is the minuend?
body: <p>At the moment I write my own little library for arithmetic and logical operations for very big unsigned integers. To improve performance I decided to implement some functions in assembly. So here is my question.
  While subtracting two unsigned integers the Carry Flag is set when I subtract any number from 0. </p>
  
  <p>But why is the Carry Flag set in this situation? The Carry Flag is only set when an overflow occurs, but if I subtract any number from zero I don't get an overflow.
  Or I am wrong?</p>