Hello and thank you for downloading the more or less podcast.

We are your weekly guide to the numbers in the news and in life, and I'm Tim Harford.

In the beginning, humanity counted on their fingers and toes.

Then came tools, scratches on a chimps thigh bone,

counting tokens, clay tablets, the Abacus.

The the Abacus. The Slide Rule dominated for over 300 years reshaping the world.

The steam train, the Hoover Dam, the Empire State Building. But all these calculating

devices were simply setting the stage for what would come after. This week I am

privileged to interview Keith Houston, the author of Empire of the Sum, the rise and rain of the pocket calculator.

So the first practical calculator, the first practical

mechanical calculator came out of France. This was invented by a man named Charles

Zavier Toma and he was an accountant effectively. He had this need to do lots of

relatively simple but quite repetitive mathematical operations. So he invented something called the arithmometer and it took

him about 30 years to perfect. From the outside it's difficult to see the difference

between his machine and the ones that had gone before, but he just refined the internals, the gearing, the mechanisms that caused it to work.

And it was reliable, and I think there are arithmometers where you can add up to sort of you know 16 digit numbers or more.

His company over his lifetime I think made about a thousand arithmometers.

It was recognised as the first mechanical calculator with any real level of commercial success selling during the second

half of the 19th century.

But it was hardly a pocket calculator.

It took up a whole desk.

That changed thanks to an Austrian Kurt Stark who needed something more

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