the Therac-25

programmingops culture

A 1980s radiation-therapy machine whose software defects delivered massive overdoses to patients.

A race condition let a fast operator trigger a high-power mode with the beam-shaping hardware out of position, and the removal of physical interlocks in favor of software checks meant nothing caught it; at least six patients were severely injured or killed. It is the canonical case study in software safety and why life-critical systems cannot trust software alone.

Also known as: Therac-25, radiation therapy accidents

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