One of the wisdoms I got from my education at HP Germany was "quality is tested into hardware". And with any real software, it is exactly the same. Or maybe should I say "even worse" ? The biggest investment is always testing, bug fixing, validation programs, test vectors, test vector generators, code reviews and so on. Initially the HP MPE operating system was very unreliable, but decades of bug fixing and refining made it into one of the most reliable operating systems.