title: Subtraction of 2 negative integer (two's complement) never overflowing
body: <p>I came across this in a computer architecture textbook:</p>
  
  <blockquote>
    <p>Subtracting a strictly negative integer from another strictly negative integer (in two's complement) will never overflow.</p>
  </blockquote>
  
  <p>The textbook doesn't go on to explain this assertion. It piqued my curiosity. </p>
  
  <p>Why is this statement true?</p>