After recreating the 19thcentury inventor's Difference Engine No. 2, a British team aims to have a go at Babbage's Analytical Engine, the 'first computer' that was never built.

British researchers announced plans this week to finally build Charles Babbage's Analytical Engine, a gear-based proto-computer conceived of but never constructed by the 19th century inventor. The Science Museum of London team, led by former museum curator Doron Swade and programmer John Graham-Cumming, says the project will take a decade and cost millions of dollars.

Swade led the effort to build two working replicas of Babbage's Difference Engine No. 2 over the past two decades. The first, completed in 1991, resides in the Science Museum and the other, commissioned a few years ago by former CTO of Microsoft Nathan Myhrvold, is a prime attraction at the Computer History Museum in Mountain View, Calif. Swade and his team face a more daunting task in attempting to build Babbage's Analytical Enginebut the payoff could be even greater.

Babbage (1791-1871) kept copious and detailed notes for his Difference Engine designs, essentially serving up a final blueprint for the Science Museum team to follow in building Difference Engine No. 2. But Babbage's ideas for the Analytical Engine, a much more complex machine, were never finalized, though several different blueprints do exist.

"There is no single set of plans that design a single machine." Tim Robinson, a docent at the Computer History Museum, told The New York Times. "It was constantly in a state of flux."

While the Difference Engine was a remarkable accomplishment of precision and elegance, it is essentially just a larger and more advanced version of the calculating machines conceived of by Babbage predecessors like Blaise Pascal and Johann Helfrich Muller.

The Analytical Engine designs, on the other hand, are regarded by many as the first in history to describe a programmable computerdrawn up by Babbage nearly a century before Alan Turing and John von Neumann codified the essential qualities of a computational device that could process and perform essentially any sort of computational task through the use of algorithms.

Babbage's Analytical Engine marked what Swade has called "the essential transition from calculation to computationfrom the mechanized arithmetic of the Difference Engine to programmable general-purpose computationthe principles of which he embodied in the designs for the Analytical Engine." Designed to be a punch-card programmed, steam-powered computing behemoth measuring 90 feet long by 30 feet wide, the engine possesses "memory" that can store 1,000 numbers of 50 digits each.

Babbage's separation of the memory, which he called "the store," from the Analytical Engine's "mill," or processor, "foreshadowed von Neumann's scheme that has dominated computer architectures in the electronic era," according to Swade. Babbage's Analytical Engine designs "incorporate most of the essential logical features commonly found in a present-day general-purpose digital computer," he added.

MORE: Lessons from the recreation of Difference Engine No. 2.

A Colossal Undertaking If Swade and his team adhere to the principles that guided them while building the Difference Engine No. 2, a decade may be an optimistic timeline for recreating the Analytical Engine.

Here's what I wrote about that process for CRN when the second replica of Difference Engine No. 2 was unveiled at the Computer History Museum in May 2008:

"Australian computer scientist and historian Allan Bromley began decoding the drawings for Difference Engine No. 2 in 1979. Six years later, Bromley, who has since died, presented himself to the then-new curator of computing at London's Science Museum, Swade (pictured at right cranking Difference Engine No. 2), with a proposalto build the thing. After a failed first attempt to build a trial piece, a small section of the machine was successfully built in 1989 and the race to build a complete Difference Engine No. 2 was on.

"The team that conceived of and built a working engine nearly 17 years after Bromley first proposed doing so included Bromley himself, Swade, Science Museum engineering curator Michael Wright and staff member Peter Turvey, and Rhoden Partners engineers Reg Crick and Barrie Holloway."

Part of the reason for the length of that process was that in building Difference Engine No. 2which weighs five metric tons, measures 11 feet long by 7 feet tall, with a depth ranging from 18 inches to 4 feet, and has 8,000 individual parts making up the three main sections of the machinewas that the materials used "were agonized over and chosen as faithfully as possible to match those that would have been available to Babbage in his era."

Swade's team had metallurgists analyze parts from Babbage's earlier machines. The builders fiercely debated "the proper mix of metals and elements for the gunmetal, cast iron and steel parts to be fabricated."

All that sweat and anxiety resulted in a working calculation machine that can be hand-cranked to calculate and tabulate any seventh-order polynomial to 31 decimal places and simultaneously print those results to on a paper roll that is part of the engine's printing and stereotyping apparatus (Swade is pictured at right cranking the first Difference Engine No. 2 at the Science Museum).

Babbage's Peers and Predecessors Babbage is not the only figure who deserves credit for the advance of mechanical calculation or even for designing a proto-computer well before its time. In fact, he built upon the work of several predecessors like Wilhelm Schickard (1592-1635), whose "Speeding Clock" machine is regarded as the first mechanical calculator, Pascal (1623-1662), who built about 50 of his "Pascaline" calculators during his lifetime, and Gottfried Wilhelm Leibniz (1646-1716), who added multiplication and limited division to Pascal's earlier invention with his "Stepped Reckoner."

Contemporaries or near-contemporaries of Babbage in the advancement of mechanical calculation included Muller (1746-1830), a Hessian army engineer who came up with the idea of a mechanical "difference engine" that produced a hard copy output of its calculations, though like Babbage, Muller never constructed his invention. Charles Xavier Thomas de Colmar (1785-1870) had better luck, patenting the "Arithometer," a calculator that could add, subtract, multiply, and even divideand which remained in production through the first years of the 20th century.

But the most famous figure associated with Babbage's loftiest dreams was his sometime collaborator, London-born Augusta Ada Byron King, Countess of Lovelace (1815-1852), the first child of the poet Lord Byron and his wife Annabella.

Lovelace is credited with the creation of the first "computer program," a sequence of calculations intended for Babbage's proposed Analytical Engine. Babbage himself described her as "The Enchantress of Numbers" and Lovelace has been somewhat mythologized in "steam punk" literature for the instruction set she is believed to have devised for calculating Bernoulli numbers with the Analytical Engine, but also for a reputation as a bewitching and beguiling prodigy of a steam-powered age.

Sadly, the forward-thinking Lovelace, who may have imagined the possibility of artificial intelligence in the mid-19th century, died as a result of archaic medical malpractice, having been bled to death in an attempt to treat her uterine cancer.