> Another problem was that I used several different ways to do the same thing in the code, without being clear about why. For example, I declared some parameter

> Another problem was that I used several different ways to do the same thing in the code, without being clear about why. For example, I declared some parameters as constants and others (which weren’t being changed) as variables — mostly because I was being sloppy. That's why C or especially C++ is probably the worst possible language to teach programming. Also, be frank with your students from the beginning about one thing: there are areas that they should understand, and then there are areas that they should just treat as "magic" and not go into, on a certain level of development. Not because they're really magic, but just keep first things first.