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.