The same method has assisted the reliability of designs in other branches of engineering, namely the use of mathematics to calculate the parameters and check, the soundness of a design before passing it for construction and installation. Shigeru Igarashi and Bob Floyd revived the idea some 20 years ago, providing the groundwork for a wide and deep research movement aimed at developing the relevant mathematical techniques. Yet, as far as I know, no one has ever checked a single safety-critical program using the available mathematical methods. What is more, I have met several programmers and managers at various levels of a safety-critical project who have never even heard of the possibility that you can establish the total correctness of computer programs by the normal mathematical techniques of modelling, calculation and proof. Such total ignorance would seem willful, and perhaps it is.
People working on safety-critical projects carry a heavy responsibility.
If they ever get to hear of a method which might lead to an improvement in reliability, they are obliged to investigate it in depth. This would give them no time to complete their current projects on schedule and within budget. I think that this is the reason why no industry and no profession has ever voluntarily and spontaneously developed or adopted an effective and relevant code of safe practice. Even voluntary codes are established only in the face of some kind of external pressure or threat, arising from public disquiet, fostered by journals and newspapers and taken up by politicians. A mathematical proof is, technically, a completely reliable method of ensuring the correctness of programs, but this method could never be effective in practice unless it is accompanied by the appropriate attitudes and managerial techniques.