Question

1985-1987 - Therac-25 medical accelerator. A radiation therapy device malfunctions and delivers lethal radiation doses at several medical facilities. Based upon a previous design, the Therac-25 was an "improved" therapy system that could deliver two different kinds of radiation: either a low-power electron beam (beta particles) or X- rays. The Therac-25's X-rays were generated by smashing high- power electrons into a metal target positioned between the electron gun and the patient. A second "improvement" was the replacement of the older Therac-20's electromechanical safety interlocks with software control, a decision made because software was perceived to be more reliable. What engineers didn't know was that both the 20 and the 25 were built upon an operating system that had been kludged together by a programmer with no formal training. Because of a subtle bug called a "race condition," a quick-fingered typist could accidentally configure the Therac-25 so the electron beam would fire in high-power mode but with the metal X-ray target out of position. At least five patients die; others are seriously injured.

• What was the impact of this bug?
• Who's to blame?
• When in the process did this bug likely get introduced (design/implementation/testing/etc.)?
• Could this bug have been avoided? How?
• Where does our responsibility begin and end as software designers, users, managers, and business people?

WRITE YOUR ANSWER WITH A MINIMUM OF 150 WORDS PLEASE!

Answer 1

Impact - The electron beam fires in high-power mode
but with the metal X-ray targets out of position. At least five patients died and others are seriously injured

Two software faults were to blame. One, when the operator incorrectly selected X-ray mode before quickly changing to electron mode, which allowed the electron beam to be set for X-ray mode without the X-ray target being in place. A second fault allowed the electron beam to activate during the field-light mode, during which no beam scanner was active or target was in place.

The design and implementation with The equipment control task did not properly synchronize with the operator interface task, so that race conditions occurred if the operator changed the setup too quickly. This was missed during testing since it took some practice before operators were able to work quickly enough to trigger this failure mode.

this bug could have been avoided by employing a programmer with formal training since  that, both the 20 and the 25 were built upon an operating system that had been kludged together by a programmer with no formal training Because of a subtle bug called a "race condition." could have been avoided which could have  avoided the Bug

Identifying, defining and communicating roles and responsibilities is fundamental to a team’s ability to deliver. A clear definition of responsibilities allows each team member to focus on their work and provides the structure needed for them to feel comfortable in their role.

Key responsibilities:

1. Initiate the project
2. Provide the project/product vision and strategy
3. Sign off key milestones