Harvard Mark II

The Harvard Mark II, also known as the Aiken Relay Calculator, was an electromechanical computer built under the direction of Howard Aiken at Harvard University. Completed in 1947, it was one of the earliest and most advanced computers of its time. The project was financed by the United States Navy and the machine was mainly used for ballistic calculations at Naval Proving Ground Dahlgren.

This remarkable machine used relays and switches to perform calculations, marking an important step in the development of modern computing. Many computer pioneers contributed to its creation, including Edmund Berkeley and Grace Hopper, who worked together under Aiken to build and program the Mark II. The Harvard Mark II showed how large-scale automatic calculation could be achieved, paving the way for future advances in computer technology.

Overview

The contract to build the Mark II was signed with Harvard in February 1945, after the successful demonstration of the Mark I in 1944. It was completed and delivered to the US Navy Proving Ground at Dahlgren, Virginia in 1948.

The Mark II was much faster than its predecessor, using high-speed electromagnetic relays. It was very large, weighing 25 short tons and occupying over 4,000 square feet. It could perform addition in 0.125 seconds and multiplication in 0.750 seconds, making it faster for both tasks compared to the Mark I. A special feature of the Mark II was its built-in hardware for complex functions like square roots and logarithms. It also had two sub-computers that could work together or separately to check results.