title: Why does a 32-bit OS support 4 GB of RAM?
body: <p>Just reading some notes in a <a href="http://www.cs.purdue.edu/homes/cs354/LectureNotes/CS354-part1.pdf" rel="noreferrer">purdue lecture about OSs</a>, and it says:</p>
  
  <blockquote>
    <p>A program sees memory as an array of
    bytes that goes from address 0 to 2^32-1 (0 to
    4GB-1)</p>
  </blockquote>
  
  <p>Why 4 GB?</p>