It seems to me like a big part of this would depend on a stable foundation. And in the software world, that foundation shifts a lot. Last I checked, no one in

It seems to me like a big part of this would depend on a stable foundation. And in the software world, that foundation shifts a lot. Last I checked, no one in the industry had come together and agreed on a list of programs that would never be changed again. And even if you could stabilize it all, how long would it be before you're forced to port it to new hardware? The moment anything shifts, any validation work you've done is called into question. Okay, for 30 seconds, your program was proven correct; but how about now? Did the change cause a problem? And how, exactly, would you detect it, without repeating the validation entirely? To me, this does underscore the importance of keeping programs small, stable, and well understood. If anyone's bragging about how many millions of lines of code they have, as Microsoft put in a bullet point for Windows once, they should not be considered serious programmers. The bigger something is, the less it takes to introduce one of these unvalidated quirks.