Boolean Algebra

In 1985, The Science Museum in London(actually an updated version that Babbage designed in 1849) and a printer (also designed by the guy). The calculation section of the Engine alone consisted of 4,000 parts (this more sophisticated design called for a third of the parts required for the first version of the Engine) and weighed 2,600 kg (5,700 lb). It was completed and working in November 1991. Impressively, the machine was accurate to 31 decimal places!

Interesting fact: one of the reasons that Babbage never completed his Difference Engine was that he couldn’t help but to continuously tinker with and improve the design (he came up with the idea for the Analytical Engine even before he could build the Difference Engine). This was probably the first recorded instance of
In 1847, self-taught British mathematician George Boole invented a branch of algebra that dealt with logic. In Boole’s system, logic operations can be boiled down to three steps: union (OR), intersection (AND), and complementation (NOT). Boole’s idea was brilliant – but at the time, it was criticized and completely ignored by his contemporaries.

It was not until almost 100 years later that in 1938, engineer Claude Shannon realized that Boolean algebra could be applied to two-valued electrical switching circuits. Shannon’s work, and by extension, that of George Boole, became the foundation of modern day digital circuit design and was the basis for all digital electronics
In 1941, despite financial hardship and isolation from computer scientists from other Western countries, German computer pioneer Konrad Zuse created the world’s first programmable computer, the Z3, from spare telephone parts.

The Z3 uses 2,000 relays (an electric switch) and was used to design aircrafts. Zuse’s request to create an electronic successor for the machine was denied by Germany as "strategically unimportant." The original Z3 was destroyed in air raid of Berlin, so Zuse built a fully-functioning replica later in the 1960s.