In Lectura 7A of SICP[1], Sussman opens the lecture by talking about how programs can be thought of as character-stream descriptions of a wiring-diagram for some kind of machine. And he actually goes on to talk about the notion of visual programming languages (he didn't think they were a good idea). It's interesting to see these screenshots of visual languages. I must say that I agree with Sussman's reasoning for not liking them (difficult to edit them and they take up a lot of real-estate).

[1] http://ocw.mit.edu/courses/electrical-engineering-and-comput...