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The Difference Engine: Charles Babbage and the Quest to Build the First Computer

Doron Swade · 4 HN comments
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Amazon Summary
A portrait of early nineteenth-century mathematician Charles Babbage describes his efforts to construct the first computing machine more than one century before the invention of the modern computer. Reprint.
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I just finished reading The Difference Engine yesterday, an entire book about this project, by the project lead!

https://www.amazon.com/Difference-Engine-Charles-Babbage-Com...

(unfortunately overshadowed in Google Search results by a William Gibson book of the same name)

It gives a lot of color on Babbage, but yes the conclusion was that Babbage design basically worked, and could have been built. There were errors in his drawings that they had to correct, but nothing fundamental.

The group at the Science Museum spent over 6 years doing this! This is the group that holds most of his papers, drafts, and unfinished machines.

Although there are a couple things I want to follow up on. They weren't that specific about what computation they did. And does it still work today? It was extraordinarily finicky. It produced a lot of bit errors, as did mechanical computing devices that came later, which sort of defeated the purpose (it was supposed to calculate tables of logarithms and such with higher accuracy than humans.)

garmaine
They require tolerances that could be achieved in the day, but not reliably was certainly not standard practice. When the funding was cut they were basically running a research program to develop better machining. With the research program failed to bad project management is kind of irrelevant. My point was it was still in the area of being a research program.
azernik
The examples built do indeed keep on working with non-prohibitive maintenance - the 2nd #2-design engine (built in the 2000s for Nathan Myhrvold), was on display at the CHM in Mountain View for 8 years with daily or twice-daily demonstration runs. It sadly went off display in 2016 (probably to go to Myhrvold's private collection) but I saw the demonstration a couple of times and can answer some of your questions:

1. The concrete computation performed was to use the Finite Difference Method (https://en.wikipedia.org/wiki/Finite_difference_method - hence the "Difference Engine" name) to calculate arbitrary polynomials of degree up to IIRC 10. By using Taylor Series, this method could be used to calculate arbitrary functions, like log and sine. This was in fact the same method used to construct logarithmic tables by hand at the time, and had similar nominal precision; the singular goal was to eliminate the bit errors rampant in the old, manual process.

2. The machine removed not just errors in calculation, but also in typesetting; about half the part-count of the original design was in its printer, which could be configured with all kinds of options for typesetting the results. It would output a "print preview" onto paper locally (this was not publicly demonstrated at the CHM because of the enormous mess of ink spills, but the machinery was run dry), and an identical wax mold ready for use in mass printing. This was because many of the bit errors in the existing log/sine/etc. tables were introduced not by the (human) computers, but by the multiple copying steps involved in transforming calculated values into printed pages.

3. Computation was quite reliable - the machine worked in base 10, and mechanisms were carefully designed to freeze up (and be easily resettable to a known-good state, as demonstrations showed) before introducing errors. As far as I know bit errors were unheard of in the demonstration runs. This reliability, like in later electronic computation, was the motivation for using digital rather than analog logic. (Finickiness was mostly limited to those halting conditions - it proved quite sensitive to clock speed (rate of crank turn), but only by the standards of the hand cranking used in demonstrations; connected up to a steam engine with 19th-century rate governors, input power could have been kept clean enough to run with long MTTF.)

gugagore
Thanks for those details. I am glad to have seen the demonstration. I didn't know they removed it in 2016.

I believe the better link is https://en.wikipedia.org/wiki/Divided_differences

There's a book that was published about 13 years ago by the man leading the program to rebuild the difference engine for London's Science Museum called, "The Difference Engine: Charles Babbage and the Quest to Build the First Computer" [1].

I can't really recommend it, since half (or more) of it is about Doron Swade navigating the politics of a London Museum in order to get the thing built. But there is an interesting history of Babbage.

[1] http://www.amazon.com/The-Difference-Engine-Charles-Computer...

paulgerhardt
Ironically a lot of the works on Babbage go into his own trials and tribulations when trying to fundraise his Difference Engine and navigating the politics of 19th Century British Government affairs.

Jacquard's Web [1] was a good break from this tradition and goes into the technical foundations for Babbage's work - highlighting the loom industry in Lyons but primarily focusing on Babbage and Lovelace's technical efforts.

My two favorite quotes from this book:

  Babbage does not himself use the words 'programming' or
  'program'. These terms had not yet entered the language and 
  he is therefore obliged to resort to more obscure
  expressions. For example, he describes the Analytical 
  Engine as being made 'special' for the mathematical 
  formula in question. In precisely the same way, we could 
  visualize a Jacquard loom that was programmed to weave a 
  lily as being made 'special' for the task of lily-weaving.
And:

  Babbage also borrowed from the Jacquard loom the plan of 
  creating what he describes as a 'library' of cards that 
  carry out different functions, with the Analytical Engine's 
  operator being able to take cards from the library as 
  required and input them into the machine in order to make it 
  special for the task. The enormous advantage of the Jacquard 
  loom was, of course, precisely that it was able to weave any 
  picture or pattern for which a chain of cards had been made. 
  Weavers would keep these chains of cards in a storeroom 
  whose function was very much the same as that of the 
  library–or we might even say software library–which Babbage 
  was proposing to create.
[1] http://www.amazon.com/Jacquards-Web-Hand-Loom-Birth-Informat...
theoh
This is a good account by Swade if you have IEEE access: The Construction of Charles Babbage's Difference Engine No. 2

http://www.computer.org/csdl/mags/an/2005/03/man2005030070-a...

Time to show my age here!

Others have listed some great, entertaining reads already:

Hackers,

Soul Of A New Machine (which won a Pulitzer),

Cringley's PBS series Triumph Of The Nerds (available on YouTube),

Where Wizards Stay Up Late

Some not mentioned so far (as I write):

The ancient, online Jargon File is a large glossary that captures a lot of early computer subculture through its lexicon. Eric S. Raymond maintains it today, but it originated way back in the 1970s: http://www.catb.org/jargon/html/

"American Experience," on PBS, did a stellar documentary on the origins of Silicon Valley and the pervasive startup mentality there. It's all about the rise of the semiconductor industry, starting with transistors. Watch online: http://www.pbs.org/wgbh/americanexperience/films/silicon/

Dropping LSD was, it turns out, crucial to the origins of personal computing! This I learned from Jaron Lanier and Kevin Kelly, who recommended John Markoff's What The Dormouse Said: http://www.amazon.com/What-Dormouse-Said-Personal-Computer-e...

The Difference Engine: Charles Babbage and the Quest to Build the First Computer is a short book but also a fun read. Doron Swade, technology historian and assistant director of London's Science Museum, races to build a copy of Charles Babbage's "difference engine" before the anniversary of said machine; he tells his travails in building it while giving Charles Babbage's story at the same time: http://www.amazon.com/Difference-Engine-Charles-Babbage-Comp...

No one has mentioned books covering the dark side of hacking. There are some great reads out there, and infosec is a crucial part of computer history.

CYBERPUNK: Outlaws and Hackers on the Computer Frontier covers Kevin Mitnick, the Chaos Computer Club, and Robert Tappin Morris (who, somewhat inadvertently, wrote the first Internet worm). Mitnick disputes his section of the book, but it's fascinating nonetheless. Worth it for the Morris part alone: http://www.amazon.com/CYBERPUNK-Outlaws-Hackers-Computer-Fro...

The Cuckoo's Egg: Tracking a Spy Through the Maze of Computer Espionage by Clifford Stoll is a fun read. Stoll is an astronomer by trade, and his analytical thinking can be an inspiration: http://www.amazon.com/The-Cuckoos-Egg-Tracking-Espionage/dp/...

The Watchman is a true crime thriller you won't be able to put down. The author set out to write a book on Mitnick but wound up detouring to do a story on Kevin Poulsen, who is now an excellent infosec writer at Wired. You will not believe what Poulsen does in this book. http://www.amazon.com/Watchman-Twisted-Crimes-Serial-Poulsen...

The Hacker Crackdown by acclaimed sci fi author Bruce Sterling is a great work on an infamous cross-country bust of many hackers. You'll get a look into the BBS subculture, Phrack Magazine, and the phreaker scene. http://www.amazon.com/Hacker-Crackdown-Disorder-Electronic-F...?

And let's not forget gaming:

Masters of Doom: How Two Guys Created an Empire and Transformed Pop Culture gives a great history of ID Software and the origins of the FPS: http://www.amazon.com/Masters-Doom-Created-Transformed-Cultu...

Sep 16, 2010 · wicknicks on Babbage's Debugger
You can read the books by Doron Swade to know more about Babbage and his machine.

http://www.amazon.com/Difference-Engine-Charles-Babbage-Comp...

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