The exact quote:
“No one will need more than 637KB of memory for a personal computer. 640KB ought to be enough for anybody.” ~ Bill Gates, 1981
Worth noting that in the same year, William Gibson's short story
Johnny Mnemonic* was published, in which the titular character was being pursued by bad guys for the hundreds of megabytes stored in his head. Which, given how much can be stuffed into a USB stick these days, seems laughably quaint now.
In the grand scheme of things, that Gates quote isn't too embarrassing compared with some of the classic predictions that pre-dated it...
“Where a calculator on the ENIAC is equipped with 18,000 vacuum tubes and weighs 30 tons, computers of the future may have only 1,000 vacuum tubes and perhaps weigh one and a half tons.” ~ Popular Mechanics, 1949
“The world potential market for copying machines is 5,000 at most.” ~ quoth IBM to the eventual founders of Xerox in 1959
“There is no reason for any individual to have a computer in his home.” ~ Ken Olsen, founder of Digital Equipment Corp, 1977.
Source:
https://www.freecodecamp.org/news/worst-tech-predictions-of-the-past-100-years-c18654211375/*
There's a film based on the story, you say? Nope, that's just a mass hallucination. Joking apart, I can't help thinking that said cinematic turkey is one of the reasons why a film adaptation of Neuromancer has never made it out of development hell.