the Canadian-built Therac-25 radiation therapy machine was designed to treat cancer patients in two different modes: either with a low-power beam of electrons or with a high-power beam of megavolt X-rays that was kept on target by a special shield. Unfortunately, unverified buggy software occasionally caused technicians to deliver the megavolt beam when they thought they were administering the low-power beam, and without the shield, which ended up claiming the lives of several patients.
