Who she was
Augusta Ada King, Countess of Lovelace, usually called Ada Lovelace, was born in London in 1815. She was the only legitimate child of the poet Lord Byron, who left the family soon after her birth. Her mother, Annabella Milbanke, arranged for her to receive an unusually thorough education in mathematics for a woman of her class and time. In her late teens she met Charles Babbage, a mathematician and inventor, and the two kept up a friendship and correspondence for many years. Lovelace died in 1852 at the age of 36.
The machines Babbage designed
Babbage is known for two designs. The Difference Engine was a special-purpose machine for producing mathematical tables using the method of finite differences. The more ambitious Analytical Engine, which he began to design in the 1830s, was meant to be a general-purpose machine. It would have a “store” for numbers and a “mill” that carried out operations, and it would be controlled by sequences of punched cards, an idea borrowed from the Jacquard loom, which used cards to control woven patterns.
Neither machine was completed in his lifetime, because of funding problems, the demands of precision manufacturing and disputes. Parts and drawings survive, and in the late twentieth century a Difference Engine was built from his plans and worked. The Analytical Engine has never been completed as a full machine, so no program for it was ever run on the original.
The notes of 1843
In 1842, an Italian engineer, Luigi Menabrea, published a description in French of a lecture Babbage had given in Turin about the Analytical Engine. Lovelace translated it into English, and at Babbage’s suggestion she added her own notes, labeled A to G. They were published in 1843 under the initials A.A.L. The notes were considerably longer than the text they accompanied.
Several ideas in the notes are frequently highlighted:
- A machine beyond numbers. Lovelace observed that the engine operated on symbols according to rules, and that those symbols need not stand for quantities. She suggested that, in principle, it could work with other things, giving music as an example, if the relations between them could be expressed. This is often cited as a forward-looking idea about general-purpose computing.
- The Jacquard comparison. She wrote that the engine weaves algebraic patterns just as the Jacquard loom weaves flowers and leaves, a vivid way of explaining the role of the cards.
- Limits on machine originality. She wrote that the engine had no pretensions to originate anything, and could only do what it was told to do. Alan Turing later discussed this remark in a famous paper on machine intelligence, which is one reason it is still quoted in discussions of artificial intelligence.
- A worked example. In the last note, Note G, she set out a table of operations for calculating a sequence of numbers known as Bernoulli numbers. It is often described as the first published computer program.
The question of credit
Her reputation has swung widely. In the twentieth century she was celebrated by many as the first programmer, and the Ada programming language, developed for the U.S. Department of Defense, was named after her around 1980. At the same time, some historians have argued that the claims made for her go too far. The main points of the debate run as follows.
The case for giving her substantial credit. She wrote the notes, and they are the clearest early description of what a general-purpose computing machine could do. Note G was a complete published example with a layout of operations and variables. Her insight about symbols and her cautions about the limits of machines showed an understanding that went beyond pure arithmetic.
The case for caution. Babbage had already worked out many programs for the engine in the 1830s, in the form of tables of operations, and some historians conclude that the Bernoulli calculation was largely his, with Lovelace contributing the presentation and corrections. Letters between the two indicate that she found at least one error in the table, which suggests she checked it carefully, and her role in the final layout is generally agreed to be real, although how much was original is argued. Because the engine was never built, the program could not be tested, and the word “programmer” is also anachronistic, since the profession did not exist.
A moderate view, held by many historians, is that she was an exceptionally perceptive interpreter and expositor of the engine, that she probably contributed original ideas on what such a machine could be for, and that calling her “the first programmer” is a simplification that depends on how the term is defined. Babbage himself is also a candidate for that title under some definitions.
How she was remembered
Her notes received little attention in the nineteenth century after their publication. They were republished in 1953 in a book that drew attention to early computing ideas, at a time when electronic computers were being built, and her reputation grew with the interest in the history of the first computers. Since then she has become a popular symbol, with a day in October named in her honor to celebrate women in science and technology.
Popular accounts sometimes add dramatic details or turn her into a legend, so it is worth returning to the notes themselves. They are available in print and are surprisingly readable. What they show is an able mathematician reflecting on a machine that did not exist, and doing so with unusual clarity.