Therac-25
loreprogramminggovernance & risk
The radiation-therapy machine whose software race conditions delivered massive overdoses in the 1980s, the founding case study of software safety.
Between 1985 and 1987 the Therac-25 gave at least six patients radiation overdoses, some fatal, after its makers removed hardware interlocks and trusted software that harbored race conditions triggered by fast operator input. Nancy Leveson and Clark Turner's investigation became required reading: the failures were systemic, not a single bug, and reused code carried assumptions the new machine no longer honored. Every 'the software will catch it' argument since has had to answer to Therac-25.