title: How to create mask with least significat bits set to 1 in C
body: <p>Can someone please explain this function to me?</p>
  
  <p>A mask with the least significant n bits set to 1.</p>
  
  <p>Ex:</p>
  
  <p>n = 6 --> 0x2F, n = 17 --> 0x1FFFF  // I don't get these at all, especially how n = 6 --> 0x2F</p>
  
  <p>Also, what is a mask?</p>