ENIAC

1946 January 4

A Manual of Operation for the Automatic
Sequence Controlled Calculator

      I’ve finally completed that book Aiken instructed me to write. It’s titled “A Manual of Operation for the Automatic Sequence Controlled Calculator”, not a very snappy name, I know. It’s a five hundred paged book that’s both a history of the Mark I, and a guide to programming it. The first chapter has information about earlier calculating machines, especially those built by Pascal, Leibniz and Charles Babbage. I began with an epigraph from Babbage. Like Ada Lovelace, I understand that Charles Babbage’s analytical engine had a special quality, which I believe will distinguish the Harvard Mark I from any other computer of the time. Like Ada and Babbage’s unbuilt analytical engine, the Mark I can be programmed with new instructions, unlike the ENIAC.

ENIAC

ENIAC was built as a digital electronic computer using circuits with vacuum tubes, that solves differential equations and can perform other tasks as well. Commander Aiken had already visited ENIAC, therefore I decided to go up to Penn to see ENIAC for myself. I was unimpressed. It seems to me that the Mark I is much more practical, and Aiken agrees with me on this, because it is easily programable, whereas ENIAC could take an entire day to be reprogrammed. The end of the war brought new problems for the ENIAC as well. The machine was originally designed to perform a specific set of calculations repeatedly, but now that the need for the calculations of missile trajectory has diminished the ENIAC is being used for other tasks, such as sonic waves and weather patterns which would mean it must be reprogrammed more often. But I suppose I can see the advantages, and changes are even being made to improve the reprogramming time, and clinging to the past is not always the best option.