title: What are 16, 32 and 64-bit architectures?
body: <p>What do 16-bit, 32-bit and 64-bit architectures mean in case of Microprocessors and/or Operating Systems?</p>
  
  <p>In case of Microprocessors, does it mean maximum size of <code>General Purpose Register</code>s or size of <code>Integer</code> or number of <code>Address-line</code>s or number of <code>Data Bus line</code>s or what?</p>
  
  <p>What do we mean by saying "<code>DOS is a 16-bit OS</code>", "<code>Windows in a 32-bit OS</code>", etc...?</p>