System Description Languages

Languages for describing digital systems have two messages to convey. They must provide enough information about the behavior of the system to permit simulation, and enough information about the structure of the system to indicate how it might be built. This double requirement distinguishes system description languages from conventional programming languages and necessitates special methods for documenting the meaning of the language. Such languages have a single form, or syntax, but two meanings, or semantics. Documentation of the language requires the definition of two distinct meanings.