Full Metal Jacket: A Visual Programming Language Based on Lisp
Of course, as it has been said, a picture is worth a thousand words, but there must be a reason why diagrammatic languages have not received the acceptance as widespread as text-based languages have. Even in "obvious" cases like microcircuit design engineers prefer text-based "hardware definition languages" over diagrams. One explanation could be that human intellect has evolved in the process of perfecting means of communication and thinking, of which a language based on symbols (words) proved to be most efficient, particularly in conveying abtractions, which is exactly where pictures, being concrete,fell short.