Technology & Medicine › Industrial revolution
Babbage's Difference and Analytical Engines
1822 (Difference Engine); 1837 (Analytical Engine design)· Invention or discovery· Communication & computing
Well documentedSolid records, physical evidence or scientific consensus.
Charles Babbage's mechanical computer designs, including the Analytical Engine, the first design for a general-purpose programmable computer.
See it on the Technology & Medicine map →How it works
Printed mathematical tables used by navigators and engineers were full of human errors. In 1822 Babbage proposed a Difference Engine to calculate and print them automatically. The British government spent about £17,000, but only a fragment was built. From 1834 he designed the Analytical Engine, with a 'store' for memory, a 'mill' for processing, punched-card input and conditional branching. Neither was finished. London's Science Museum built his Difference Engine No. 2 in 1991; it worked.
Why it mattered
Babbage worked out the core architecture of a computer (memory, processor and program) about a century before electronic machines.
How we know
Thousands of his drawings and notebooks at the Science Museum, London; Menabrea's 1842 description of the Analytical Engine; and the working 1991 reconstruction.
Still unknown or debated
Could 1840s engineering have built the Analytical Engine? A volunteer project, Plan 28, is trying. Most later computer pioneers did not know his work.
Inside this (1)
Connections (4)
▸Mechanical calculators (Schickard, Pascal, Leibniz) paved the way for Babbage's Difference and Analytical EnginesMostly agreed
The connection
Seventeenth-century calculators by Schickard, Pascal and Leibniz showed that gears could add and multiply. Babbage went further: rather than help a person do one sum, his Difference Engine would compute and print whole tables automatically. His direct spur, though, was errors in hand-computed tables.
When and how
Germany and France, 1623–1673; London, 1821, when Babbage and John Herschel checked error-filled astronomical tables.
How sure are we?
Babbage's memoir, Passages from the Life of a Philosopher (1864), stresses table errors and de Prony's teams of human calculators rather than earlier machines.
Debates and open questions
How much Babbage borrowed from earlier calculator mechanisms, such as carrying tens, is unclear; his own carry mechanisms were largely new designs.
▸Jacquard loom (punched cards) lent punched cards to Babbage's Difference and Analytical EnginesWell documented
The connection
Babbage saw that Jacquard's cards stored instructions apart from the machine. He planned to feed the Analytical Engine two decks: operation cards saying what to do and variable cards saying which numbers to use. Programs could be swapped, repeated and reused, like loom patterns.
When and how
London, from about 1836, when Babbage adopted cards for the Analytical Engine; he owned a silk portrait of Jacquard woven using about 24,000 cards.
How we know
Babbage's notebooks and Lovelace's 1843 notes cite the loom: the engine 'weaves algebraical patterns just as the Jacquard loom weaves flowers and leaves.'
Debates and open questions
Whether later card users, such as Herman Hollerith's 1890 census machines, took the idea from Jacquard, Babbage or punched railway tickets is uncertain.
▸Babbage's Difference and Analytical Engines were programmed on paper by Ada LovelaceMostly agreed
The connection
Babbage explained the Analytical Engine in Turin in 1840, and Luigi Menabrea wrote it up in French. Lovelace translated the article and added notes three times longer, including a step-by-step table for computing Bernoulli numbers, a sequence used in mathematics, on the engine. It is often called the first published computer program.
When and how
London, 1842–43, in close correspondence with Babbage; published in Taylor's Scientific Memoirs, 1843, signed only 'A.A.L.'
How sure are we?
The published notes and her letters to Babbage survive, showing her drafting, questioning and correcting the work.
Debates and open questions
Babbage had sketched smaller programs years earlier, and how much of Note G's mathematics was hers versus his is debated.
▸Babbage's Difference and Analytical Engines were a century ahead of the Electronic computer (Z3, Colossus, ENIAC)Mostly agreed
The connection
Babbage's Analytical Engine had a 'mill' to calculate, a 'store' for memory, punched-card input and the ability to branch on results, the same basic layout as a modern computer. It was never built. Electronic computers rebuilt these ideas with relays and tubes instead of gears, though most of their builders had not studied him.
When and how
London, 1830s–1871 (Babbage's designs); Harvard's Howard Aiken, who built the 1944 Mark I, found Babbage's writings and saw himself as his heir.
How sure are we?
Babbage's drawings survive; London's Science Museum built a working Difference Engine No. 2 from them in 1991, proving his designs were sound.
Debates and open questions
Direct influence was small: ENIAC and Colossus engineers largely reinvented his ideas. Whether Victorian machining could have built the Analytical Engine is still argued.