“Correctness means never returning an inaccurate result; returning no result is better than returning an inaccurate result. Robustness means always trying to do something that will allow the software to keep operating, even if that leads to results that are inaccurate sometimes. Safety-critical applications tend to favor correctness to robustness. It is better to return no result than to return a wrong result. The radiation machine is a good example of this principle. Consumer applications tend to favor robustness to correctness. Any result whatsoever is usually better than the software shutting down. The word processor I'm using occasionally displays a fraction of a line of text at the bottom of the screen. If it detects that condition, do I want the word processor to shut down? No. I know that the next time I hit Page Up or Page Down, the screen will refresh and the display will be back to normal.”