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Date: Thu, 28 Jun 2012 11:03:18 -0700
From: Jerry Petrey <gpetrey@earthlink.net>
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Subject: Re: Ada in medical devices
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Date: 2012-06-28T11:03:18-07:00
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On 6/27/2012 3:10 AM, Ian Clifton wrote:
> Jerry Petrey <gpetrey@earthlink.net> writes:
>
>> On 6/21/2012 3:37 PM, Jeffrey Carter wrote:
>>>
>>> I once knew a C coder, and a mediocre C coder at that, who was coding
>>> for pacemakers. I hope I never need one.
>> How true.  Remember the Therac-25 incident in the 1980's where C
>> pointer problems killed a number of people with huge doses of X-rays?
>>
> To be fair, I believe the Therac-25 software was written in PDB-11
> assembler:
>
> http://sunnyday.mit.edu/papers/therac.pdf page 23
>


You are right.  It was written in PDP-11 assembly language - I 
remembered incorrectly.  Nancy Leveson has an excellent coverage of the 
Therac-25 accident in her book "Safeware: System Safety and Computers".
The problems were caused by coding errors and improper reuse attempts by 
trying to reuse some of the Therac-6 and Therac-20 code in the newer 
Therac-25.  It was a very sad outcome.

Jerry