I haven't had the opportunity to read all of this document, but the thing I love the most so far is that it explains the history of what led up to the birth of

I haven't had the opportunity to read all of this document, but the thing I love the most so far is that it explains the history of what led up to the birth of the OS: "With larger memories and independent I/O operation came the possibility of more efficient machine utilization. A portion of the machine could be dedicated to the programs which assisted in machine operation, the operating system. As a result, overall productivity of the system increased." The author succinctly shows how we went from calculators to hardware with an OS. A wonderful explanation.