Ada Lovelace's Notes on an engine that never ran
The September 1843 issue of Taylor’s Scientific Memoirs contained a translation of an Italian engineering paper, signed with the initials “A.A.L.” The paper was about Charles Babbage’s Analytical Engine — a proposed calculating machine that had not been built and, as things turned out, never would be. The initials belonged to Augusta Ada King, Countess of Lovelace, twenty-seven years old, daughter of Lord Byron, and the person who had just appended to that translation seven notes that were three times longer than the article itself — and rather more important.
Ada had met Babbage on June 5, 1833, introduced by the polymath Mary Somerville at one of his Saturday evening gatherings. She was seventeen. Babbage showed her a working section of his Difference Engine, and she grasped it instantly — to the point where Babbage, not a man given to easy compliments, called her the “Enchantress of Number.” Nine years later, when Charles Wheatstone commissioned her to translate Luigi Menabrea’s French transcript of Babbage’s Turin lecture, she did not simply translate. She annotated.
The seven Notes, labeled A through G, ran to roughly 65 pages. Notes A through F dealt with the Engine’s architecture and operation. Note G was different. It contained a complete algorithm — 25 operations, nested loops, careful tracking of variable states — for computing Bernoulli numbers on the hypothetical machine. Nobody had written anything like it: a precise, step-by-step procedure for solving a specific mathematical problem on a general-purpose device. The algorithm was never run, because the Engine was never built, but the structure of it was unmistakably what we now call a program.
What made Note G technically surprising was not just the algorithm but the rigor with which it was specified. Menabrea’s own examples contained no loops. Ada invented them — or at least invented their explicit notation — tracking how variable values changed across successive operations with a superscript system that any modern programmer would recognize as a precursor to assignment statements. She also introduced a counter that decremented on each loop iteration. The discipline of thinking through a computation before running it: that was new.
There was a falling-out mid-project. Babbage, irritated by the government’s refusal to fund the Engine, attempted to slip an unsigned preface into the publication criticizing officials by name. Ada refused to attach her translation to it. Their correspondence turned tense; the preface was dropped. The collaboration survived, barely.
The deeper thing Ada saw — and that Babbage had not quite articulated — was that the Engine did not have to be a calculator. It was a symbol-manipulator. “The Analytical Engine might act upon other things besides number,” she wrote in Note A, “were objects found whose mutual fundamental relations could be expressed by those of the abstract science of operations.” She went on to suggest it might compose music. She was describing, in 1843, what Alan Turing would formalize a century later: the general-purpose computer.
She died in November 1852, aged thirty-six, of cervical cancer. She was buried beside her father, as she had asked, at the Church of St. Mary Magdalene in Hucknall, Nottinghamshire. The programming language named for her was standardized in 1980; its reference manual was approved on December 10 — her birthday.
Sources
- Ada Lovelace — Wikipedia — biography, the June 1833 meeting with Babbage, the 1843 publication in Taylor’s Scientific Memoirs, Notes A–G, and her death.
- Ada Lovelace — Computer History Museum — the Babbage–Lovelace collaboration and the significance of Note G as the first published algorithm.
- What Did Ada Lovelace’s Program Actually Do? — Two-Bit History — technical analysis of Note G: the 25 operations, nested loops, variable-state tracking, and comparison to Menabrea’s simpler examples.