https://en.wikipedia.org/wiki/Harvard_Mark_II The Harvard Mark II was a relay computer, as it was around prior to the transistor it used mechanical relays to alternate current pathways. There were many other relay computers around this time, but what made the Mark II memorable over time is it was the origin for the term “Bug” in relation to computing, as in 1947 the computer was malfunctioning, the source of the malfunction turned out to be a moth that had found its way inside the machine