This is a supplementary document for Chapter 1 from my book Mac OS X Internals: A Systems Approach (see Amazon.com page). A subset (about 30%) of this document appears in the book as the first chapter with the title "Origins of Mac OS X".
The document is titled "A Technical History of Apple's Operating Systems". Whereas the book's abridged version covers the history of Mac OS X, this document's coverage is considerably broader. It encompasses not only Mac OS X and its relevant ancestors, but the various operating systems that Apple has dabbled with since the company's inception, and many systems that were direct or indirect sources of inspiration.
This was the first chapter I wrote for the book. It was particularly difficult to write in terms of the time and other resources required in researching the material. I often had to find and scavenge ancient documentation, software, and hardware (all actual screenshots shown in this document were captured first hand.) However, I couldn't include the chapter in its original form in the book. The book grew in size beyond everybody's expectations—1680 pages! Therefore, it was hard to justify the inclusion of this much history, even if it is interesting history.
I strongly believe that reading this document will be helpful in understanding the evolution of Mac OS X, and to some extent, of some aspects of modern-day operating systems. An important reality of technology, and of computing in particular, is that many things that we think of as "new ideas" are not quite new. As Alan Kay once said, "Most ideas come from previous ideas." This is also true in the case of Mac OS X. As one digs the past of Mac OS X and its predecessors, one begins to understand how ancient things influenced not-so-ancient things, and the fact that we owe what we have today to a lot more people than are usually credited.