THERAC 25 CASE STUDY PPT

Social Implications of a Computerized Society – Have we become too dependent on computers? A Gift of Fire, 2edChapter 4: Auth with social network: Encodes result in 2-byte shared variable 3. Help Preferences Sign up Log in. Professional Ethics – Whistle-blowing Continued Whistle-blowing incidents can occur because of either:

What role do safety and risk play? World’s Best PowerPoint Templates – CrystalGraphics offers more PowerPoint templates than anyone else in the world, with over 4 million to choose from. Software is easy to change. The Linear Accelerator -. Social, Legal, and Ethical Issues for Computers. View by Category Toggle navigation. Therac 20 and Therac 6 relied on hardware safety systems Therac 25 removed the hardware safety Therac 25 software had the same bugs as found in Therac 20 9 Testing of Therac 25 As software came from Therac 20 it was assumed to be bug free AECL assumed only hardware failures were possible as software doesnt degrade over time AECL performed a safety analysis on the Therac and apparently excluded the software.

Computers reduce risk over mechanical systems.

therac 25 case study ppt

The computer suggests an action, informs the operator, and implements the action if not stopped in time. We’ll even convert your presentations and slide shows into the universal Flash format with all their original multimedia glory, including animation, 2D and 3D transition effects, embedded music or other audio, or even video embedded in slides.

A patient has complained that he has received a radiation overdose during a treatment session caused by the malfunctioning of the Therac unit.

Reusing software increases safety.

Software Safety Case Study Medical Devices : Therac 25 and beyond Matthew Dwyer.

In spite of problems, computers and other technologies have made air travel safer Software Engineering, Fall Lecture 2: Position patient on treatment table 3. World’s Best PowerPoint Templates – CrystalGraphics offers more PowerPoint templates than anyone else in the world, with over 4 million to choose from. This is a medical machine that fires high energy radiation to destroy tumors.

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therac 25 case study ppt

You can use PowerShow. An Investigation of the Therac Accidents.

Feedback Privacy Policy Feedback. Formal Verification of Computer Systems – Civil engineering. The cost of computers is lower than that of analog or electromechanical devices. A Software Fatal Failure. Parses text input 2. Products Sold on our sister site CrystalGraphics. Project Management Software Reuse Disasters: Use rapid prototyping languages and tools Increasing software reliability will increase safety.

Detects data entry 2. Leveson et al, 10 Failure of risk assessment AECL did not perform a proper risk assessment of Therac 25 Hardware would be the primary cause of failure Believed overdosing of patients was impossible 11 Software issues Used flags to synchronise processes Used 8-bit flags which were prone to overflowing Created race condition between magnet control and keyboard control The error messages were indecipherable to users technicians 12 Implications If the user entered any data while the gun was being set it did not react However the rest of the system did react, allowing unshielded X-Rays to be fired A race condition in a real-time system!

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Software Safety Case Study Medical Devices : Therac 25 and beyond Matthew Dwyer. – ppt download

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But you have no idea what it is. Therac 20 and Therac 6 relied on hardware safety systems Therac 25 studt the hardware safety Therac 25 software had the same bugs as found in Therac 20 9 Testing of Therac 25 As software came from Therac 20 it was assumed to be bug free AECL assumed only hardware failures were possible as software doesnt degrade over time AECL performed a safety analysis on the Therac and apparently excluded the software.

therac 25 case study ppt

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Clarke to refer to the Software for Critical Systems – Increased use of critical software is irresistable How do we make decisions about uncertain events?