Preface
To Everyone
Welcome to this book! We hope you’ll enjoy reading it as much as we enjoyed
writing it. The book is called Operating Systems: Three Easy Pieces (available
at http://www.ostep.org), and the title is obviously an homage to one of the
greatest sets of lecture notes ever created, by one Richard Feynman on the topic of
Physics [F96]. While this book will undoubtedly fall short of the high standard set
by that famous physicist, perhaps it will be good enough for you in your quest to
understand what operating systems (and more generally, systems) are all about.
The three easy pieces refer to the three major thematic elements the book is
organized around: virtualization, concurrency,andpersistence. In discussing
these concepts, we’ll end up discussing most of the important things an operating
system does; hopefully, you’ll also have some fun along the way. Learning new
things is fun, right? At least, it should be.
Each major concept is divided i nto a set of chapters, most of which present a
particular problem and then show how to solve it. The chapters are short, and try
(as best as possible) to reference the source material where the ideas really came
from. One of our goals in writing this book is to make the paths of history as clear
as possible, as we think that helps a student understand what is,whatwas,and
what will be more clearly. In this case, seeing how the sausage was made is nearly
as important as understanding what the sausage is good for
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There are a couple devices we use throughout the book which are probably
worth introducing here. The first is t he crux of the problem. Anytime we are
trying to solve a problem, we first try to state what the most important issue is;
such a crux of the problem is explicitly called out in the text, and hopefully solved
via the techniques, algorithms, and ideas presented in the rest of the text.
In many places, we’ll explain how a system works by showing its behavior
over time. These timelines are at the essence of understanding; if you know what
happens, for example, when a process page faults, you are on your way to truly
understanding how virtual memory operates. If you comprehend whattakesplace
when a journaling file system writes a block to disk, you have taken the first steps
towards mastery of storage systems.
There are also numerous asides and tips throughout the text, adding a little
color to the mainline presentation. Asides tend to discuss something relevant (but
perhaps not essential) to the main text; tips tend to be general lessons that can be
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Hint: eating! Or if you’re a vegetarian, running away from.
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