Ada Lovelace

Ada Lovelace

Augusta Ada King, Countess of Lovelace (1815–1852)
Personal details
Born	10 December 1815, London
Died	27 November 1852 (aged 36), London
Parents	Lord Byron and Anne Isabella Milbanke
Work
Known for	Notes on the Analytical Engine; the first published algorithm
Collaborator	Charles Babbage

Augusta Ada King, Countess of Lovelace (10 December 1815 – 27 November 1852), known as Ada Lovelace, was an English mathematician who worked on Charles Babbage's proposed Analytical Engine. Her notes on the machine contain what is generally regarded as the first published algorithm intended to be carried out by a machine, and a clear statement that such a machine could operate on things other than numbers.

Lovelace was the only legitimate child of the poet Lord Byron and Anne Isabella Milbanke. Her parents separated weeks after her birth and she never met her father. Her mother, herself mathematically trained, arranged an unusually rigorous education in mathematics and science, in the declared hope of suppressing any tendency towards the poetic temperament she blamed for Byron's conduct. Lovelace's tutors included Mary Somerville and Augustus De Morgan.

Lovelace met Charles Babbage in 1833 and saw a working portion of his Difference Engine, a machine for computing polynomial tables by repeated addition. Babbage's later design, the Analytical Engine, was far more ambitious: a general-purpose mechanical computer with a "mill" for arithmetic, a "store" for numbers, and control by punched cards borrowed from the Jacquard loom. It was never built in his lifetime.

In 1842 the Italian mathematician Luigi Menabrea published a description of the engine in French. Lovelace translated it, and at Babbage's suggestion appended notes of her own, labelled A to G. The notes ran to roughly three times the length of the original paper and were published in 1843.^[1]

Note G sets out, step by step, how the engine would compute the Bernoulli numbers, including the arrangement of operations, the reuse of intermediate results, and a loop repeating a group of operations with changing values. Presented as a table of operations rather than as code in any modern sense, it is nonetheless a program: a complete specification of a computation for a machine to perform. It is on this basis that Lovelace is often called the first computer programmer, a description historians have variously endorsed and qualified, since the program was written in close collaboration with Babbage and never run.

Note G also contains her judgement on the machine's limits:

The Analytical Engine has no pretensions whatever to originate anything. It can do whatever we know how to order it to perform.

— Ada Lovelace, Note G, 1843

Alan Turing addressed this passage directly a century later in his 1950 paper on machine intelligence, calling it "Lady Lovelace's objection" and arguing that a machine can surprise its programmer often enough for the claim to lose its force.

What most distinguishes the notes is Note A, where Lovelace observes that the engine's operands need not stand for quantities at all. If the relationships between pitches in harmony, for instance, could be expressed in the engine's notation, then the machine might compose music of any complexity. She was describing general-purpose symbolic computation a century before a machine existed that could perform it, and grasping the point that Babbage, focused on calculation, largely did not: that a computer manipulates symbols, and numbers are only one thing symbols can mean.

Lovelace died of uterine cancer in 1852, aged thirty-six. Her notes attracted little attention until the mid-twentieth century, when they were reprinted as computing acquired a history. Ada Lovelace Day, marking women's contributions to science and technology, is observed in October.

• Computer
• Alan Turing

1. ^ Menabrea, L. F., with notes by A. A. L. "Sketch of the Analytical Engine invented by Charles Babbage". Scientific Memoirs, vol. 3, 1843.