Programming languages as operating systems (or revenge of the son of the lisp machine)

The MrEd virtual machine serves both as the implementation platform for the DrScheme programming environment and as the underlying Scheme engine for e xecuting expressions and programs entered into DrScheme's read-eval-print l oop. We describe the key elements of the MrEd virtual machine for building a programming environment, and we step through the implementation of a mini ature version of DrScheme in MrEd. More generally, we show how MrEd defines a high-level operating system for graphical programs.