In October 1843, Augusta Ada King, Countess of Lovelace, daughter of Lord Byron, translated Menabrea’s paper, "Notions sur la machine analytique de M. Charles Babbage" (1842). Her "Sketch of the Analytical Engine Invented by Charles Babbage . . . with Notes by the Translator" published in Scientific Memoirs, Selected from the Transactions of Foreign Academies of Science and Learned Societies 3 (1843): 666-731 plus 1 folding chart, was the first edition in English of the the first published account of Babbage’s Analytical Engine, and, more significantly, of its logical design.
In 1840 Babbage traveled to Torino to present to a group of Italian scientists an account of the Engine. Babbage’s talk, complete with drawings, models and mechanical notations, emphasized the Engine’s signal feature: its ability to guide its own operations. It also included the first computer programs though Babbage did not use that word. In attendance at Babbage’s lecture was the young Italian mathematician Luigi Federico Menabrea (later Prime Minister of Italy), who prepared from his notes an account of the principles of the Analytical Engine, which he published in French in 1842.
In keeping with the more general nature and immaterial status of the Analytical Engine, Menabrea’s account dealt little with mechanical details. Instead he described the functional organization and mathematical operation of this more flexible and powerful invention. To illustrate its capabilities, he presented several charts or tables of the steps through which the machine would be directed to go in performing calculations and finding numerical solutions to algebraic equations. These steps were the instructions the engine’s operator would punch in coded form on cards to be fed into the machine; hence, the charts constituted the first computer programs. Menabrea’s charts were taken from those Babbage brought to Torino to illustrate his talks there (Stein, Ada: A Life and Legacy, 92).
Menabrea’s paper was translated into English by Babbage’s close friend Ada, Countess of Lovelace, daughter of the poet Byron and a talented mathematician in her own right. At Babbage’s suggestion, Lady Lovelace added seven explanatory notes to her translation, which run about three times the length of the original. Her annotated translation has been called “the most important paper in the history of digital computing before modern times” (Bromley, “Introduction” in Babbage, Henry Prevost, Babbage’s Calculating Engines, xv). As Babbage never published a detailed description of the Analytical Engine, Ada’s translation of Menabrea’s paper, with its lengthy explanatory notes, represents the most complete contemporary account in English of this much-misunderstood machine.
Babbage supplied Ada with algorithms for the solution of various problems, which she illustrated in her notes in the form of charts detailing the stepwise sequence of events as the machine progressed through a string of instructions input from punched cards (Swade, The Cogwheel Brain, 165). This was the first published example of a computer “program,” though neither Ada nor Babbage used this term. She also expanded upon Babbage’s general views of the Analytical Engine as a symbol-manipulating device rather than a mere processor of numbers, suggesting that it might act upon other things besides number, were objects found whose mutual fundamental relations could be expressed by those of the abstract science of operations. . . . Supposing, for instance, that the fundamental relations of pitched sounds in the science of harmony and of musical composition were susceptible of such expression and adaptations, the engine might compose elaborate and scientific pieces of music of any degree of complexity or extent (p. 694) . . . Many persons who are not conversant with mathematical studies, imagine that because the business of the engine is to give its results in numerical notation, the nature of its processes must consequently be arithmetical and numerical, rather than algebraical and analytical. This is an error. The engine can arrange and combine its numerical quantities exactly as if they were letters or any other general symbols; and in fact it might bring out its results in algebraical notation, were provisions made accordingly (p. 713).
Much has been written concerning what mathematical abilities Ada may have possessed. Study of the published correspondence between her and Babbage (see Toole 1992) is not especially flattering either to her personality or mathematical talents: it shows that while Ada was personally enamored of her own mathematical prowess, she was in reality no more than a talented novice who at times required Babbage’s coaching. Their genuine friendship aside, Babbage’s motives for encouraging Ada’s involvement in his work are not hard to discern. As Lord Byron’s only legitimate daughter, Ada was an extraordinary celebrity, and as the wife of a prominent aristocrat she was in a position to act as patron to Babbage and his engines (though she never in fact did so).