One thing that I think a lot of introductions are missing is an extremely simple first model of a Von Neumann style computer. I teach the undergrad computer systems class and two models I have found extremely useful are:

- But How Do It Know/Scott CPU (https://www.youtube.com/watch?v=HeYAtkbHvuQ&list=PLYE0XunAbw...)

- The Little Man Computer (https://www.youtube.com/watch?v=9AWN_ntHfPk)

Especially these days, where the computer is more and more abstract from students experience, i think these tangible, visual tools are important for them to get a feel for what's going on at the lowest level of computation (at least in some sense)