An accessible guide to our digital infrastructure, explaining the basics of operating systems, networks, security, and other topics for the general reader.

Mark Stuart Day


Mark Stuart Day was Chief Scientist at Riverbed Technology for a decade and is currently Visiting Lecturer at MIT. With more than thirty patented inventions, he has also made technical contributions at Dropbox, IBM, Cisco, Digital, and BBN.


Most of us feel at home in front of a computer; we own smartphones, tablets, and laptops; we look things up online and check social media to see what our friends are doing. But we may be a bit fuzzy about how any of this really works.

In Bits to Bitcoin, Mark Stuart Day offers an accessible guide to our digital infrastructure, explaining the basics of operating systems, networks, security, and related topics for the general reader. He takes the reader from a single process to multiple processes that interact with each other; he explores processes that fail and processes that overcome failures; and he examines processes that attack each other or defend themselves against attacks.


Quantum Digital Assistants and Silly Predictions

June 14, 2019

June is perhaps a little early to start declaring winners for the whole of 2019. Nevertheless, I’m willing to go out on a limb for a recent article in the Wall Street Journal. The article “When Quantum Computing Meets AI: Smarter Digital Assistants and More”…


Bits to Bitcoin: How Our Digital Stuff Works was published August 2018 by The MIT Press.

You can see a video of Mark's book talk at Google.

You can see video of Mark discussing the book on "It's All Write with Suzette."

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Wireless communication via WiFi can be affected by microwave ovens.

Large-scale data centers (collections of computers) generate so much heat that cooling is an important concern in where to place them. Locations in cold climates are favored, and people are starting to work seriously on putting them in the ocean.

“Bits to Bitcoin” was partly inspired by the professional textbook “Principles of Computer Systems Design” by Jerry Saltzer and Frans Kaashoek.

Bitcoin depends on a kind of “computational treadmill” that repeatedly solves hard puzzles.

The total energy spent on Bitcoin puzzle-solving is constantly growing. Bitcoin’s energy consumption is already estimated to be larger than the total energy consumption of Chile.

The Internet is composed of many different networks, each with different ownership and control. The “seams” between these networks are usually not visible to ordinary users.

Relationships between networks in the Internet are like relationships between nation states. The relationships are negotiated between the networks, and are primarily enforced by the participants.

In general, a digital representation is more robust than a corresponding analog representation against low levels of interference and noise.

As noise worsens, analog systems typically have a noticeable transition into “noisy” operation before they stop working. In similar circumstances, digital systems generally make sharper -- and possibly more surprising -- transitions from “working” to “not working,” with little warning.