1. A system for machine-assisted programming of a target processor which can execute a target programming language, comprising: input means and graphical display means for displaying graphical images in accordance with interactive input by an operator; storage means for storing a representation of a program for said target processor, said program representation being expressed in a definition language; means operatively coupled to said display means, said input means and said storage means for editing said program representation by interactive manipulation of said displayed graphical images; means operatively coupled to said storage means for providing a simulation of an external environment of said target processor, and for simulating execution of said program by said target processor as if said program were expressed in said target programming language and including simulation of interaction of said target processor with said simulation of said environment in accordance with said program; means operatively coupled to said display means, said storage means and said simulation means for displaying said simulated execution of said program; and translation means operatively coupled to said storage means for translating said program representation in said definition language into a corresponding representation in said target programming language.