This report introduces the programming system PISA intendei for the interactive production of application software. The heart of the programming system is a new programming language, also called PISA. An interactive environment for this language permits the creation, test, maintenance, and usage of PISA programs in a real-time dialogue fashion. Both the programming language and its interactive environment are described without any reference to a specific implementation. Together, they form a well defined programming system whose components interact harmoniously. The programming system PISA is dedicated to application software production. This implies that production of system software and online-control programs is not a goal of PISA. Furthermore, it means that PISA must meet several requirements as they arise from commercial application software production, the most stringent ones being economy, availability, and compatibility: In the long term the overall cost of software production and usage with such a programming system must be less than with conventional means, the programming system must be available or implementable on a wide range of computer systems currently used, and existing data must be accessible in its actual physical representation. The definition of PISA is given in a heavily annotated form in this report: Examples for the use of single componer.ts as well as for the entire system are presented, most of the lan uage constructs and system facilities are commented on briefly, and the implications of the programming system’s design on implementability and portability issues are discussed.