Graphical representations of programs have been tried too, and all such attempts have been failures. (I was a project manager for such an attempt in the 80s.) The basic problem is that a program is naturally a high-dimensional object, and when mapped down into a two dimensional picture it is about as comprehensible as a bowl of spagetti.

The problem has consitently appeard to me to be related to the use of incorrect abstractions. Most of the visual attempts I've seen have been roughly equivalent to printing binary code to screen as an attempt for a textual representation of a program. I'm still (very optimistically) waiting for a video-game which tackles this problem succesfully (some of the FF series ones have done an ok job).