Abstract We present, from a user's point of view, an overview of the PSG system, a generator for semantics-based programming environments. The PSG system generates an interactive, language-specific environment from a complete formal language definition. Both the syntax, as well as the static and dynamic semantics of the language are specified in the definition. The definition is used to generate a context-sensitive hybrid editor and an interactive interpreter with debugging facilities. The paper describes the structure and the main features of PSG-generated environments, as well as the design decisions which led to the development of the PSG environment.