<i>I&#x27;ve told my students that if you can&#x27;t run the program in your head, then you simply don&#x27;t understand what&#x27;s going on. You haven&#x27;t learned anything.</i><p>Absolutely. A coworker has a similar version of that line, which I&#x27;ve committed to memory:<p>&quot;If you don&#x27;t understand precisely what you need to do, what makes you think you can tell a computer how to do it?&quot;<p>I also briefly taught programming, and that&#x27;s a line I&#x27;ve used more often than I&#x27;d like. Another thing I&#x27;ve noticed is that IDEs tend to encourage beginners to perform much random fiddling of code that doesn&#x27;t work, often creating a mess in the process.