Ada Lovelace

Ada Lovelace was an English mathematician and writer, the daughter of the poet Lord Byron, best known for her work on Charles Babbage's Analytical Engine, a mechanical computer that was designed but never built. Her 1843 notes on the machine included a detailed procedure for calculating a series of numbers, often described as the first published computer program, and suggested that such machines could handle music and symbols as well as arithmetic. How much of the mathematics was her own has been debated, but her vision of what computers might do was well ahead of its time.

She was born Augusta Ada Byron in London on 10 December 1815, the only legitimate child of Lord Byron and Anne Isabella Milbanke. The marriage collapsed within weeks of her birth. In January 1816 her mother left with the baby, and in April Byron signed a deed of separation and left England for good. He died in Greece in 1824, when Ada was eight, and she never knew him.

Lady Byron, who had a strong interest in mathematics herself, was determined that her daughter should not inherit what she saw as her father's dangerous temperament. She had Ada taught mathematics and science from an early age, partly as a form of mental discipline, and arranged for trusted friends to watch the girl's behaviour. Ada was often ill. Measles in 1829 left her unable to walk properly for a long period, and she used crutches until about 1831. As a twelve-year-old she nevertheless designed a flying machine, studying bird anatomy and planning a book she called Flyology.

Ada was taught by private tutors, among them the social reformer William Frend and, most importantly, the scientific writer Mary Somerville, who became a friend. In the 1840s the mathematician Augustus De Morgan guided her through advanced calculus by correspondence and told her mother that she might become an original mathematical investigator of the first rank. She described her own approach as poetical science, a mix of rigour and imagination.

In 1833, aged 17, she was presented at court. On 5 June that year Somerville took her to one of Babbage's Saturday evening parties in London, where he showed a working fragment of his Difference Engine, a machine for calculating mathematical tables. She was fascinated, and the two began a long friendship. Through society and science she also came to know Michael Faraday, Charles Wheatstone and the novelist Charles Dickens. In 1835 she married William King, who was made Earl of Lovelace in 1838, so that she became Countess of Lovelace. They had three children, born between 1836 and 1839.

Babbage's later design, the Analytical Engine, was far more ambitious than the Difference Engine. Using punched cards borrowed from the Jacquard loom, a technology of the Industrial Revolution, it was to have a store for numbers, a separate unit for performing operations, and the ability to repeat steps and to choose different paths depending on its results. In 1840 Babbage described it at a meeting in Turin, in the Kingdom of Sardinia, and a young engineer, Luigi Menabrea, later prime minister of Italy, wrote an account in French that was published in 1842.

Wheatstone asked Lovelace to translate Menabrea's paper into English. Working closely with Babbage over nine months, she added seven notes, labelled A to G, that ended up about three times as long as the article itself. They appeared in Taylor's Scientific Memoirs in 1843, signed only with her initials, A.A.L. The last, Note G, set out step by step how the engine could calculate Bernoulli numbers, a sequence that appears in number theory, with a table tracing every operation and variable. Because the engine was never built, the procedure was never run, although later analysis found it would essentially have worked, apart from a small error.

What most distinguishes the notes is their argument about what the engine was. Lovelace wrote that it could act on anything whose relationships could be expressed in symbols, not only numbers, and imagined it composing elaborate pieces of music if the rules of harmony were encoded for it. Babbage himself thought chiefly about calculation, and her idea of a general symbol-processing machine anticipates the modern understanding of computing.

She also set out a limit. The engine, she wrote, had no pretensions to originate anything and could only do what it was ordered to do. A century later Alan Turing discussed this point at length in his 1950 paper on machine intelligence, calling it Lady Lovelace's objection, and it is still cited in debates about artificial intelligence.

After the notes, Lovelace hoped to continue scientific work and spoke of building a calculus of the nervous system, a mathematical account of how the brain produces thought, but she produced nothing further of substance. In the late 1840s she became involved in gambling on horse races, and around 1851 a betting scheme run with male friends left her heavily in debt, which she had to confess to her husband. She developed cancer of the womb and endured months of painful illness, during which her mother controlled who could visit her. She died in London on 27 November 1852, aged 36, the same age as her father at his death, and at her own request was buried beside him at Hucknall in Nottinghamshire.

Lovelace was largely forgotten until her notes were reprinted in 1953, when early electronic computers were being built in the United Kingdom and the United States. Since then she has become a symbol of women in science and technology. In 1980 the United States Department of Defense named its new programming language Ada, and since 2009 Ada Lovelace Day has been held each October to celebrate women in science.

Historians disagree about how far she deserves the title of first programmer. Babbage had written examples of programs for the engine between 1837 and 1840, before her notes, and in his memoirs he claimed some of the work on the Bernoulli calculation, though he said she had found a serious mistake in it. Some scholars, such as Dorothy Stein, have argued that her mathematical abilities were modest and that Babbage did much of the substantive work. Others, citing her letters, see her as a capable mathematician who understood the machine's possibilities more clearly than almost anyone of her time, Babbage included. Most agree that the Analytical Engine itself had no direct influence on the electronic computers of the 20th century, which were developed independently.