The moment they can read. Sure you can literally define structures and processes before that, but doing the real deal on a computer before you can read... is g

The moment they can read. Sure you can literally define structures and processes before that, but doing the real deal on a computer before you can read... is going to be a disaster. You need to read your own code to get your bearings of where you are in the file. Anything more complex than 5 instructions is a no-go for non-readers.