The introduction is terrific reading.
He starts by talking about restaurants in his neighborhood of Manhattan, particularly a very popular one called Isabella’s:
Here’s a clue as to why Isabella’s works. In ten years living in this neighborhood, I still go back there. All the time. Because they’ve never given me a single reason not to.
That actually says a lot.
Then he talks about other restaurants that have lots of problems, even though the food may be better than Isabella’s. And then he says:
Eventually, Isabella’s became a fabulously profitable and successful restaurant, not because of its food, but because it was debugged. Just getting what we programmers call “the edge cases” right was sufficient to keep people coming back, and telling their friends, and that’s enough to overcome a review where the New York Times calls your food “not very good.”
Great products are great because they’re deeply debugged. Restaurants, software, it’s all the same.
Great software doesn’t crash when you do weird, rare things, because everybody does something weird.
Microsoft developer Larry Osterman, working on DOS 4, once thought he had found a rare bug. “But if that were the case,” he told DOS architect Gordon Letwin, “it’d take a one in a million chance for it to happen.”
Letwin’s reply? “In our business, one in a million is next Tuesday.”