The Therac-25 Incident

Re:The Therac-25 Incident by po on Wednesday November 29, 2023 @08:14AM (#38458933)

I first learned of this incident in the early 2000s from a computer book about how to code UML State charts in C/C++ [1]. It included a CD-ROM with a library that implemented a rather clever way of maintaining state using the call stack.

Unfortunately, the naive software fix for the Therac-25 is to add a flag (which is additional state) to the system which is to add complexity to the system.

[1] https://www.state-machine.com/doc/PSiCC.pdf

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Re:The Therac-25 Incident by elromulous on Wednesday November 29, 2023 @08:30AM (#38459085)

We had a term for implicit state machines at a place I used to work: infinite flag machines[0].

[0] I suspect the majority of hn folks are familiar with finite state machines, but just in case: https://en.m.wikipedia.org/wiki/Finite-state_machine

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