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...

The worst part is that many devlopers think that by not working with high integrity systems, such quality levels don't apply to them.

Wrong, any software failure can have huge consequences in someone's life, or company, by preventing some critical flow to take place, corrupting data related to someone's life, professional or medical record, preventing a payment on some specific goods that had to be acquired on that moment or never,....

Hey don’t blame developers.

It is business who requests features ASAP to cut costs and and then there are customers who don’t want to pay for „ideal software” but rather have every software for free.

Most devs and QA workers I know want to deliver best quality software and usually are gold plating stuff anyway.

Being a real Software Engineer, those that actually have the proper title, eventually with the final examination, means being able to deliver the best product within the set of given constraints.

Also, speaking out when the train is visibly going against a wall.