scott wrote:

> Of course there are, but far less than in desktop software.  My point 
> was that depending how much effort you want to put in to it, you either 
> end up with software like Microsoft, software like Nasa, or somewhere 
> inbetween.

NASA?

Aren't they those guys who tried to launch a rocket with a faulty O-ring?

Mmm, I guess it's not only M$ that sometimes rushes things due to 
"launch shedules".

(You see what I did there?)

>> I'm sure there are glitches in the firmware of cars, you probably 
>> don't notice, or think its something mechanically wrong.
> 
> It's extremely unusual though, almost unheard of, for there to be any 
> noticeable glitch in the core software running a car.  It's simply 
> because the consequences are so great, that the effort is put in to 
> ensure that no glitches ever can occur.  Especially nowadays with all 
> the stability, engine and other control stuff run by software, it would 
> be a total disaster for any company if their cars suddenly did something 
> stupid under certain conditions.

Depends on how "stupid". I hear there's a car (I forget which) that has 
a design fault so anybody who knows the "trick" can open the boot with 
their bare hands even when it's locked - yet the manufacturers 
repeatedly refused to admit that anything was wrong...

> I saw a solid steel drive bar approx 10cm diameter sheared in two by a 
> motor, it was meant to be driving a machine to compress paper, but it 
> got jammed and for some reason the controller didn't stop the motor but 
> kept giving it more power.

I saw a machine that can casually snip through 30 mm spring steel the 
way a hole punch cuts through tissue paper. The operator commented 
"don't put your fingers in this". (!!)

> But if you knew your software was to control something like a car or 
> plane with people in it, you would have course checked and tested your 
> software more thoroughly.  That's my original point, ditto with Andrew's 
> order, if they really cared enough they would have systems in place to 
> make sure that incorrect orders could not be delivered.

This is what it all comes down to. You can make things as reliable as 
you want - it's merely a question of how much money you want to spend 
doing it. ;-)

> But usually there are 4 totally separate controllers, so they do have a 
> high degree of redundancy.

...I also saw a black-box flight recorder yesterday...

(It was orange.)

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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