Double-click was added to the Apple Lisa computer in 1980 to overcome a small problem: The computer had only a single button. The single-button was a defensible decision in 1980. It was no longer defensible after around 1985, but, at least on Macs, the decision has persisted, much to the detriment of Mac users.

Meanwhile, Microsoft was engaged in wholesale copying of the Mac interface. People at Microsoft did understand that a multi-button mouse was superior, but failed to understand why double-clicking was there in the first place, so they slavishly duplicated it.

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