This is a working Difference Engine No. 2 at the Computer History Museum in Mountain View, Calif.

Charles Babbage designed a Difference Engine, which is one of the earliest computation machines — some would say the first programmable computer — in the 1840s. He went on to create an improved design, the Difference Engine No. 2, but never built one in his lifetime.

Babbage’s designs were finally built by engineers working for the London Science Museum, with funding from former Microsoft chief technology officer Cameron Myhrvold in 1989 to 1991. But he stipulated that they had to build him a second one in exchange for the funding. He loaned it to the Computer History Museum. Volunteers maintain the pure steel rods so that they don’t rust. This particular machine was finished in 2008.

It’s a particularly inspiring piece of machinery. And it shows how much trouble people went to in order to come up with the calculations that we now take for granted. It’s a reminder of how far we have come and how much technology is at our fingertips in the machines that we have today.

The Difference Engine is supposed to calculate logarithmic tables. Mathematicians, engineers and scientists relied on these tables for navigation and measurements, but Babbage was concerned that human-created tables were always subject to tiny errors that could produce disastrous results. We shot a little video of the Difference Engine No. 2 in action at the museum, which is celebrating the launch of its $19 million Revolution exhibit on Thursday. After he designed the engine, Babbage added a printer that is shown in the two subsequent videos below. The printer types on paper or on a stereotype tray, which you could flood with liquid metal to make a printing plate with.