A Victorian computer revolution

Imagine a Victorian England where the computer revolution arrived 100 years early. That’s the picture painted in the novel The Difference Engine by William Gibson and Bruce Sterling.

Electronics were still a distant dream, so the computers in this alternative history had cogs and gears instead of silicon chips, and were driven by steam engines rather than electricity.

Surprisingly, this isn’t as far-fetched as it sounds. The machines these authors envisaged bringing information technology to the Victorian age were grounded firmly in reality.

Mathematician and engineer Charles Babbage described his “Analytical Engine” back in 1834. Despite its mechanical nature, this is widely considered to have been the first computer as we now understand the word. Babbage never actually built the Engine; but if he had, could it have paved the way for a computer revolution at the same time as the industrial revolution?

The Analytical Engine

Much of what we know about the Analytical Engine makes sense to us today. Like modern processors, it had internal registers – in one version, 100 such stores – each with a precision of 50 decimal digits. Also, like a modern-day computer, it was designed to manipulate that data using instructions that would be executed sequentially. These, and the data on which they operated, were supplied on punch cards.

Computer historians believe that the Analytical Engine had most of the essential features of a universal computer, as defined by Alan Turing a century later.

The Engine was documented by Augusta Ada King, the Countess of Lovelace and the daughter of poet Lord Byron, – now usually simply referred to as Ada Lovelace. Her interest in science, and a chance meeting with Babbage, led to her fascination with the Analytical Engine.

In describing Babbage’s invention, Lovelace published what many consider the first ever algorithm, which has led to her being dubbed the world’s first computer programmer. Indeed, her programs can be recognised as such today, being a list of instructions that are usually executed sequentially but which can also be executed repeatedly in loops. The Engine would even have permitted the sequence of executions to alter, depending on the outcome of earlier instructions – conditional branching, in today’s language.

Despite the obvious similarity with modern computers, the Analytical Engine differed phenomenally in its sheer scale. To perform such a feat using mechanics, the Engine would have required 50,000 individual parts, and the completed unit would have been 15m long by 5m tall, with the “mill” – the CPU in today’s terms – being around 2.5m in diameter. It would have weighed 40 tonnes.

It isn’t clear how Babbage imagined powering this beast, but it’s hard to imagine that it could have been driven by hand, which has led some to suggest that he envisaged using a steam engine.

Sadly, due to a lack of funding, Babbage never built the Analytical Engine and his plans were left unproven for more than a century.