&gt; The portability of a language is best understood as how difficult&#x2F;expensive it is to port a conforming program written in the language in question.<p>What proportion of the things that are referred to in ordinary, everyday language as &quot;C programs&quot; would you estimate are conforming? Maybe 0.01%? If I&#x27;d meant &quot;conforming C code&quot; I would&#x27;ve said &quot;conforming C code&quot;.<p>Writing conforming C is not a realistic choice for most use cases. E.g. there are very few experienced conforming C developers available.