Part 3/6:
As the treatment began, the Therac-25 displayed a "Malfunction 54" error, indicating a dose input error. The operator, having operated the machine for over 500 patients, pressed the "Pause" button to reset the system, unaware of the severity of the issue.
Unbeknownst to the operator, Ray Cox had already received a massive overdose of radiation, estimated to be between 16,000 and 25,000 RADS, instead of the prescribed 180 RADS. In the following weeks, Ray Cox would suffer excruciating pain and paralysis, ultimately succumbing to his injuries five months later.
The Flaws in the Therac-25's Software
The root cause of the Therac-25's deadly flaw lay in its software design and the underlying assumptions about software reliability.