Z3, First Working Programmable Computer

In 1941, Konrad Zuse created the first dependable computer. It was binary but contained floating point number capability. Programming was done with punched film.

The computer was still largely mechanical, but Zuse was able to get rid of the Babbage's gears by using telephone switching relays. Before the advent of digital switching, when people dialed a phone number, each number they dialed opened a relay that took them one step closer to opening a circuit to the final destination. Dial "1" and the "1" relay was opened. Dial "5" and the "5" relay is opened. In short, each telephone's open line resulted in a unique combination. In the Zuse computer, the combinations lead to numerical solutions.

This was done in Austria during WWII, and it should have been a benefit to the Nazis, but according to some historians, Americans and British bombers destroyed his early machines. Other historians suggest that Hitler dropped the project because he believed that the war was all but won, and he would not need the power of the computer. Next

Circuit switching works by having switches dedicated to specific numbers. Each telephone has a unique combination of switches.