Even if a child does not fully understand everything, the child DOES understand that when they type an instruction, the computer will execute it! This is exciting, akin to finally getting that the squiggles on paper are words and letters, even if you don't know them and can't quite read them yet. The next step is to build up concepts, like executing steps in a loop, or storing information and getting it later, or starting and stopping. This is all worthwhile, even if you can't quite see it from where you are standing.