This is the fourth edition of "Distributed Systems." We have stayed close to the setup of the third edition, including examples of (part of) existing distributed systems close to where general principles are discussed. For example, we have included material on blockchain systems, and discuss their various components throughout the book. We have, again, used special boxed sections for material that can be skipped at first reading. The text has been thoroughly reviewed, revised, and updated. In particular, all the Python code has been updated to Python3, while at the same time the channel package has been almost completely revised and simplified. Additional material, including coding examples, figures, and slides, are available at www.distributed-systems.net.

From 1983 to 1986, the legendary physicist and teacher Richard Feynman gave a course at Caltech called “Potentialities and Limitations of Computing Machines.”Although the lectures are over ten years old, most of the material is timeless and presents a “Feynmanesque” overview of many standard and some not-so-standard topics in computer science. These include computability, Turing machines (or as Feynman said, “Mr. Turing's machines”), information theory, Shannon's Theorem, reversible computation, the thermodynamics of computation, the quantum limits to computation, and the physics of VLSI devices. Taken together, these lectures represent a unique exploration of the fundamental limitations of digital computers.Feynman's philosophy of learning and discovery comes through strongly in these lectures. He constantly points out the benefits of playing around with concepts and working out solutions to problems on your own-before looking at the back of the book for the answers. As Feynman says in the lectures: “If you keep proving stuff that others have done, getting confidence, increasing complexities of your solutions-for the fun of it-then one day you'll turn around and discovers that nobody actually did that one! And that's the way to become a computer scientist.”

"In The Second Self, Sherry Turkle looks at the computer not as a 'tool,' but as part of our social and psychological lives; she looks beyond how we use computer games and spreadsheets to explore how the computer affects our awareness of ourselves, of one another, and of our relationship with the world. 'Technology,' she writes, 'catalyzes changes not only in what we do but in how we think.' First published in 1984, The Second Self is still essential reading as a primer in the psychology of computation. This twentieth anniversary edition allows us to reconsider two decades of computer culture - to (re)experience what was and is most novel in our new media culture and to view our own contemporary relationship with technology with fresh eyes. Turkle frames this classic work with a new introduction, a new epilogue, and extensive notes added to the original text. Turkle talks to children, college students, engineers, AI scientists, hackers, and personal computer owners - people confronting machines that seem to think and at the same time suggest a new way for us to think - about human thought, emotion, memory, and understanding. Her interviews reveal that we experience computers as being on the border between inanimate and animate, as both an extension of the self and part of the external world. Their special place betwixt and between traditional categories is part of what makes them compelling and evocative. (In the introduction to this edition, Turkle quotes a PDA user as saying, 'When my Palm crashed, it was like a death. I thought I had lost my mind.') Why we think of the workings of a machine in psychological terms - how this happens, and what it means for all of us - is the ever more timely subject of The Second Self." -

Man has within a single generation found himself sharing the world with a strange new the computers and computer-like machines. Neither history, nor philosophy, nor common sense will tell us how these machines will affect us, for they do not do "work" as did machines of the Industrial Revolution. Instead of dealing with materials or energy, we are told that they handle "control" and "information" and even "intellectual processes." There are very few individuals today who doubt that the computer and its relatives are developing rapidly in capability and complexity, and that these machines are destined to play important (though not as yet fully understood) roles in society's future. Though only some of us deal directly with computers, all of us are falling under the shadow of their ever-growing sphere of influence, and thus we all need to understand their capabilities and their limitations. It would indeed be reassuring to have a book that categorically and systematically described what all these machines can do and what they cannot do, giving sound theoretical or practical grounds for each judgment. However, although some books have purported to do this, it cannot be done for the following a) Computer-like devices are utterly unlike anything which science has ever considered---we still lack the tools necessary to fully analyze, synthesize, or even think about them; and b) The methods discovered so far are effective in certain areas, but are developing much too rapidly to allow a useful interpretation and interpolation of results. The abstract theory---as described in this book---tells us in no uncertain terms that the machines' potential range is enormous, and that its theoretical limitations are of the subtlest and most elusive sort. There is no reason to suppose machines have any limitations not shared by man.