2013: Advent Computing: A historical divergence: Babbage and Lovelace

by on December 10, 2013

A line drawing showing many interlocking cogs and wheels, some with numbers and indicators marked on them, with a hand crank at the top

A small part of the difference engine, via Wikipedia

Back in the 18th century, a “computer” was a person who performed computations. They would calculate mathematical tables by hand – long lists of numbers that could be referenced for calculations. It would be a slow and arduous process prone to error, but was vital for the sciences, particularly astronomy.

The first computers as we understand them were only theoretical. Charles Babbage designed his “difference engine” in 1822, which would solve polynomial equations by turning a crank, either by hand or by steam. The device was never produced at the time, due to the complexity of the mechanics and Babbage coming up with a better idea.

Babbage first described his “analytical engine” in 1837. Unlike the difference engine, which could only really perform addition, the analytical engine could also subtract, multiply, divide, take square roots and compare two numbers. More importantly, it was designed to be “programmable”, to be adjusted to solve assorted problems rather than one specific one. Mechanical looms at the time used punched cards of paper to control them, so Babbage took the same trick for his computer.

Working with Babbage, Ada Lovelace designed what is often cited as the first computer program, designed for this machine, leaving her credited as the first computer programmer.

The analytical machine was “Turing complete”, that is, it could do anything a Turing machine could do, even though the concept didn’t exist at the time. While it would require a hand crank, a long time, the analytical machine could do anything a modern computer could do. Modern computers have far more memory than the analytical machine was designed for, but that just means the analytical machine would need to be really big.

Sadly, the analytical engine was never built either, much to the chagrin of the British government who were funding it. The first mechanical calculator that made it to production was Thomas de Colmar’s Arithmomètre, and programmable computers wouldn’t appear until after the turn of the century.

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