>>>Gerry-
>>>
>>>>"Theoretically" it is possible to have bug free code. Given enough time, _anything_ is possible; eg. "Big Bang".
>>>
>>>Nope. Impossible to _prove_. Impossible to test in all contexts on all systems under all conditions. Even your example. However, I did qualify my comments to Jim by saying a program of sufficient complexity to be useful.
>>
>>I'll give you a function that's possible to prove that may look impossible. Try this (very simple)

FUNCTION AddTwo
>>  LPARAMETERS tnOne, tnTwo
>>
>>  RETURN tnOne + tnTwo
>>ENDFUNC

>
>
>>> program of sufficient complexity
>
>...and then the idea is that if you can build a whole out testable parts then you can validate the entire whole as 100% defect free. There's a couple of problems with that approach. But I think I've pretty much already made my point.

Yep, you have. My point here is that, in strictly my view, folks don't do the basic testing of their algorithms (prove them).

>And one of them seems to have been lost. That quality does count. But "defect free" is like "mom and apple pie." *shrug*

Frankly, under the conditions we work, I'd say that it was impossible to be able to prove that a system was defect free. The problem isn't on the individual developer end. Rather it's on the combination of individual developers. I don't know that so-and-so developed to the specs. If he did, then my proof is valid. If he didn't....< s >