This paper describes a new input language for behavioral synthesis called EXEL. EXEL is a powerful language that permits the user to specify partially designed structures in the language. It employs a mixed graphic/textual user interface to enhance user interactivity. EXEL's design model is comprehensive: it permits specification of synchronous and asynchronous behavior, and allows specification of general timing constraints. A flexible type construct permits the user to define operators and components to be used in the description. Finally, it simplifies compilation by using a small set of constructs for specifying timing and asynchronouos behavior. The compiler for EXEL runs on SUN-3 workstations and is written in C and SUNVIEW
