Modular, Behaviour Preserving Extensions of the Unix C-shell Interpreter Language

The Unix C shell interpreter language shall be used to explore an approach of modular language descriptions and extensions. Based on a language core, language features are added stepwise on the core. Features can be described separated from each other in a self-contained, orthogonal way. Existing dependencies among the features can be represented by sequential ordering. The presented framework facilitates the stepwise development or extension of languages. Adapting basic constructs for an extended language is simplified by providing templates. These templates will also guarantee that properties of the basic language are preserved in the extension. Categories and Subject Descriptors: D.3.1 [Programming Languages] Formal Definitions and Theory (Semantics), F.3.2 [Logics and Meanings of Programs] Semantics of Programming Languages (Denotational Semantics), F.3.3 [Logics and Meanings of Programs] Study of Program Constructs Additional Key Words: Extension semantics, formal language engin..