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15 hours ago by Eerke Boiten If Spock would not think it illogical, its probably good code. Credit: Alexandre Buisse, CC BY-SA

Legendary Dutch computer scientist Edsger W Dijkstra famously remarked that "testing shows the presence, not the absence of bugs". In fact the only definitive way to establish that software is correct and bug-free is through mathematics.

It has long been known that software is hard to get right. Since Friedrich L Bauer organised the very first conference on "software engineering" in 1968, computer scientists have devised methodologies to structure and guide software development. One of these, sometimes called strong software engineering or more usually formal methods, uses mathematics to ensure error-free programming.

As the economy becomes ever more computerised and entwined with the internet, flaws and bugs in software increasingly lead to economic costs from fraud and loss. But despite having heard expert evidence that echoed Dijkstra's words and emphasises the need for the correct, verified software that formal methods can achieve, the UK government seems not to have got the message.

Formal software engineering

The UK has always been big in formal methods. Two British computer scientists, Tony Hoare (Oxford 1977-, Microsoft Research 1999-) and the late Robin Milner (Edinburgh 1973-95, Cambridge 1995-2001) were given Turing Awards the computing equivalent of the Nobel Prize for their work in formal methods.

British computer scientist Cliff B Jones was one of the inventors of the Vienna Development Method while working for IBM in Vienna, and IBM UK and Oxford University Computing Laboratory, led by Tony Hoare, won a Queen's Award for Technological Achievement for their work to formalise IBM's CICS software. In the process they further developed the Z notation which has become one of the major formal methods.

The formal method process entails describing what the program is supposed to do using logical and mathematical notation, then using logical and mathematical proofs to verify that the program indeed does what it should. For example, the following Hoare logic formula describing a program's function shows how formal methods reduce code to something as irreducibly true or false as 1 + 1 = 2.

Taught at most UK universities since the mid-1980s, formal methods have seen considerable use by industry in safety-critical systems. Recent advances have reached a point where formal methods' capacity to check and verify code can be applied at scale with powerful automated tools.

Government gets the message

Here is the original post:
It's possible to write flaw-free software, so why don't we?