How Many Additions Per Second Could an ENIAC Perform?

At the start of the 20th century, governments and businesses relied on special purpose computing devices, such as tabulating machines, to replace manual tasks. However, the world’s population almost doubled, and the complexity of human systems, engineering, and scientific endeavors increased. This explosion of data and bureaucracy drove the need for more automation and computation.

One of the largest electro-mechanical computers ever built was the Harvard Mark I, completed in 1944 by IBM for the Allies during World War II. It contained 765,000 components, three million connections, and five hundred miles of wire. The machine used relays, which are electrically-controlled mechanical switches, to run simulations for the Manhattan Project.

Relays have a control wire that determines whether a circuit is opened or closed. When current flows through the coil, an electromagnetic field is created, which attracts a metal arm inside the relay, snapping it shut and completing the circuit. However, the mechanical arm inside a relay has mass and cannot move instantly between opened and closed states. A good relay in the 1940s might be able to flick back and forth fifty times in a second.

The Harvard Mark I could perform three additions or subtractions per second. This was not fast enough to solve complex problems. However, this machine set the stage for future innovation, such as the Electronic Numerical Integrator And Computer (ENIAC).

The ENIAC was the first general-purpose electronic computer. It used vacuum tubes instead of relays, which allowed it to perform calculations much faster. The machine weighed thirty tons and occupied a room the size of a small house. It could perform five thousand additions per second, which was five thousand times faster than the Harvard Mark I.

In conclusion, the need for automation and computation drove the development of electro-mechanical computers like the Harvard Mark I, which used relays to perform calculations. However, the mechanical arms inside relays could not move fast enough to solve complex problems. This led to the development of electronic computers like the ENIAC, which used vacuum tubes and could perform calculations much faster.