Analytical engine

From Wikipedia, the free encyclopedia

The analytical engine, an important step in the history of computers, was the design of a mechanical general-purpose digital computer by the British professor of mathematics Charles Babbage. It was first described in 1837, but Babbage continued to work on the design until his death in 1871. Because of financial, political, and legal issues, the engine was never actually built. In its logical design the machine was essentially modern, anticipating the first completed general-purpose computers by about 100 years.

Some believe that the technological limitations of the time were a further obstacle to the construction of the machine; others believe that the machine could have been built successfully with the technology of the era if funding and political support had been stronger.

1 Design
2 Partial construction
3 Influence
- 3.1 Computer science
- 3.2 Fiction
4 Comparison to other early computers
5 External links

[edit] Design

Charles Babbage's first attempt at a mechanical computing device was the difference engine, a special-purpose calculator designed to tabulate logarithms and trigonometric functions by evaluating approximate polynomials. As this project faltered for personal and political reasons, he realized that a much more general design was possible and started work designing the analytical engine.

The analytical engine was to be powered by a steam engine and would have been over 30 meters long and 10 meters wide. The input (programs and data) was to be provided to the machine via punch cards, a method being used at the time to direct mechanical looms. For output, the machine would have a printer, a curve plotter and a bell. The machine would also be able to punch numbers onto cards to be read in later. It employed ordinary base-10 fixed-point arithmetic. There was a store (i.e., a memory) capable of holding 1,000 numbers of 50 digits each. An arithmetical unit (the "mill") would be able to perform all four arithmetical operations.

The programming language to be employed was akin to modern day assembly languages. Loops and conditional branching were possible and so the language as conceived would have been Turing-complete long before Alan Turing's concept. Three different types of punch cards were used: one for arithmetical operations, one for numerical constants, and one for load and store operations, transferring numbers from the store to the arithmetical unit or back. There were three separate readers for the three types of cards.

In 1842, the Italian mathematician Luigi Menabrea, whom Babbage had met while traveling in Italy, wrote a description of the engine in French. In 1843, the description was translated into English and extensively annotated by Ada King, Countess of Lovelace, who had become interested in the engine ten years earlier. In recognition of her additions to Menabrea's paper, which included a way to calculate Bernoulli numbers using the machine, she has been described as the first computer programmer. The modern computer programming language Ada is named in her honor.

[edit] Partial construction

In 1878, a committee of the British Association for the Advancement of Science recommended against constructing the analytical engine, which sank Babbage's efforts for government funding.

In 1910, Babbage's son Henry P. Babbage reported that a part of the mill and the printing apparatus had been constructed and had been used to calculate a (faulty) list of multiples of pi. This constituted only a small part of the whole engine; it was not programmable and had no storage.

[edit] Influence

[edit] Computer science

The analytical engine was then all but forgotten, with three known exceptions. Percy Ludgate wrote about the engine in 1915 and even designed his own analytical engine (it was drawn up in detail but never built). Ludgate's engine would be much smaller than Babbage's of about 8 cubic feet (230 L) and hypothetically would be capable of multiplying two 20-decimal-digit numbers in about 6 seconds. Leonardo Torres y Quevedo and Vannevar Bush also knew of Babbage's work, though the three inventors likely did not know of each other.

Closely related to Babbage's work on the analytical engine was the work of George Stibitz of Bell Laboratories in New York just prior to WWII, as well as Howard Hathaway Aiken at Harvard University during and just after WWII. They both built electromechanical (i.e. relay-and-switch) computers which were closely related to the analytical engine, though neither was (quite) a modern programmable computer. Aiken's machine was largely financed by IBM and was called the Harvard Mark I.

From Babbage's autobiography:

As soon as an Analytical Engine exists, it will necessarily guide the future course of the science.

[edit] Fiction

The cyberpunk novelists William Gibson and Bruce Sterling co-authored a steampunk novel of alternative history titled The Difference Engine in which Babbage's difference and analytical engines became available to Victorian society. The novel explores the consequences and implications of the early introduction of computational technology.

There is also mention of the Analytical Engine (or the Clockwork Ouroboros as it is also known there) in The Book of the War, a Faction Paradox anthology edited by Lawrence Miles. This machine was used to calculate a way into the "Eleventh Day Empire". Its use resulted in the destruction of the original Houses of Parliament.

[edit] Comparison to other early computers

If the Analytical Engine had been built, it would have been in many ways more advanced than the first computers that emerged in the 1940s. It would have been digital, programmable and Turing complete.

*Defining characteristics of five first operative digital computers*
Computer	Nation	Shown working	Binary	Electronic	Programmable	Turing complete
Zuse Z3	Germany	May 1941	Yes	No	By punched film stock	Yes (1998)
Atanasoff-Berry Computer	USA	Summer 1941	Yes	Yes	No	No
Colossus computer	UK	1943	Yes	Yes	Partially, by rewiring	No
Harvard Mark I/IBM ASCC	USA	1944	No	No	By punched paper tape	No
ENIAC	USA	1944	No	Yes	Partially, by rewiring	Yes
ENIAC	USA	1948	No	Yes	By Function Table ROM	Yes