> We will deliver defect free software every time - is this motto workable?<p>No, it isn't. It isn't because the Turing halting problem is known to be undecidable. This doesn't mean defect free software cannot be written, it means this cannot be proven.<p><a href="http://en.wikipedia.org/wiki/Halting_problem" rel="nofollow">http://en.wikipedia.org/wiki/Halting_problem</a><p>A quote: "Alan Turing proved in 1936 that a general algorithm to solve the halting problem for all possible program-input pairs cannot exist. A key part of the proof was a mathematical definition of a computer and program, what became known as a Turing machine; the halting problem is undecidable over Turing machines."<p>In layman's terms, this means a company promising defect-free software is just asking for trouble. It is to software development what an "unsinkable" ocean liner like the Titanic is to world travel.<p>> These questions are not rhetorical.<p>On the contrary, to anyone familiar with the basic principles of computer science, the question is rhetorical and the answer is "no".