The paper presents a simple programming language and rewriting system called GENS. It is based on an extension of the -calculus called E-calculus. GENS is a multiparadigm language: it has been used for definition of semantics and for implementation of functional, logical, procedural, and object-oriented languages. It also allows combining different programming paradigm styles in a single programming language. The purpose of this paper is to define and to introduce the E-calculus