Notions sur la machine analytique de M. Charles Babbage

The First Programs. First edition, the journal issue, of the first published account of Babbage's Analytical Engine - and, printed a full year before Ada Lovelace's celebrated English translation of it, the first appearance in print of computer programs: the operation-tables setting out, step by step, how Babbage's projected machine would be driven through a calculation. The paper appeared only in this Swiss journal, which survives chiefly in institutionally-stamped subscription copies; the present example is uncommon in carrying no library stamp at all. Babbage had conceived the Analytical Engine in 1834, in the aftermath of his uncompleted, government-funded Difference Engine. It was to be a general-purpose programmable calculating machine - never built in his lifetime, yet embodying in its design most of the essential features of the modern digital computer. From the Jacquard loom Babbage took control by punched cards; from the vocabulary of the textile trade he took the names of its parts, calling the processing unit the 'mill' and the memory the 'store'. Its signal feature, and the hardest for his contemporaries to grasp, was its capacity to govern its own course: to advance or back its cards according to the results of its own previous calculations - what is now called conditional branching. Babbage's countrymen showed little curiosity about the machine, and he never presented it publicly in England. The one occasion on which he set out its principles before a company of competent scientists came abroad. In 1840, pressed by the Turin astronomer Giovanni Plana (1781-1864), he travelled to the congress of Italian scientists at Turin, carrying drawings, models and sheets of his mechanical notation, and over several mornings in his apartments expounded the Engine to Plana, Menabrea, Mossotti, MacCullagh, Plantamour and others. The difficulty, as Anthony Hyman records in Charles Babbage: Pioneer of the Computer (1982), lay less in the mechanism than in the concept: Mossotti could accept that the machine handled arithmetic and even algebra, but balked at how it might take a course of action determined by its own results - until Babbage, by a series of examples, brought his listeners to see how the Engine could advance or back its operation cards by any number of steps. The Turin discussions, Hyman writes, were 'the only public presentation before a group of competent scientists during Babbage's lifetime' of the ideas behind the modern digital computer. Menabrea's account said little of mechanical detail. What it did instead was decisive: to show what the machine could do, he printed several tables - 'cartons des opérations', 'cartons des variables' - setting out the ordered sequence of operations through which the Engine would be directed to solve a given problem, from a difference-table for the series of squares to the working of a pair of simultaneous equations. These tables, reproduced from those Babbage had brought to Turin, are what Hook and Norman call 'the first examples of computer programs ever published'; Dorothy Stein, in Ada: A Life and a Legacy (1985), traces them to Babbage's own charts and likewise finds that they 'constituted the first computer programs'. They precede by a year the more famous program with which the paper is now usually associated. In 1843 Augusta Ada King, Countess of Lovelace (1815-1852), Byron's daughter, translated Menabrea's memoir into English as 'Sketch of the Analytical Engine . with Notes by the Translator' (in Taylor's Scientific Memoirs, volume 3), appending seven notes of her own, signed only 'A.A.L.', that ran to some three times the length of the original; the last, Note G, set out a method for computing the Bernoulli numbers that is often - though the attribution is contested - called the first algorithm written for a computer. That fuller, later program built directly upon the operation-tables first printed here. Plana had meant to write up the lectures himself, but he was old a.…