I used to help teach kids (12-16ish) how to code.

One thing that we always did towards the beginning of a class was an exercise where we tell them to write down the steps to make a peanut butter and jelly sandwich. Then we'd literally get bread, peanut butter, and jelly, and follow their instructions to the letter. No one ever adequately describes the process: "put peanut butter on bread" - With what? the jar is closed, I can't! etc.

You might argue this introduces too imperative a thought process - but it gets the "computers do exactly what you tell them to" idea across very well.