The Therac-25 Incident (2021)

> software quality doesn't appear because you have good developers. It's the end result of a process, and that process informs both your software development practices, but also your testing. Your management. Even your sales and servicing.

If you only take one thing away from this article, it should be this one! The Therac-25 incident is a horrifying and important part of software history, it's really easy to think type-systems, unit-testing and defensive-coding can solve all software problems. They definitely can help a lot, but the real failure in the story of the Therac-25 from my understanding, is that it took far too long for incidents to be reported, investigated and fixed.

There was a great Cautionary Tales podcast about the device recently[0], one thing mentioned was that, even aside from the catasrophic accidents, Therac-25 machines were routinely seen by users to show unexplained errors, but these issues never made it to the desk of someone who might fix it.

[0] https://timharford.com/2025/07/cautionary-tales-captain-kirk...

I worked for a company that manufactured some of the highest-Quality photographic and scientific equipment that you can buy. It was expensive as hell, but our customers seemed to think it was worth it.

> It's the end result of a process

In my experience, it's even more than that. It's a culture.

A culture of high-quality engineering, no doubt. Made up of: high quality engineers!

you don't need "high quality engineers" to have high-quality outputs. And vice-versa - lots of places with very high quality engineers produce terribly low-quality software

> you don't need "high quality engineers" to have high-quality outputs.

[citation needed]

37signals and craigslist are two examples (and they’re open about their engineering being sub-par). If you consider FB products “high quality”, it’s another example (the average FB developer is anything but “high quality”, by most definitions). Palantir is another example, with a horde of junior engineers and famous for bad practices (yet here they are commanding the US military). And so on and so on. The inverse is also true - plenty of stellar teams producing irrelevant or low impact products.