The aim of this paper is to introduce and validate the concept of program working storage (PWS) as a) a means of smooth transition of students in introductory programming courses from the end-user stance to the programmer stance, and b) a system which can provide comprehensive understanding of certain difficult programming concepts. In this respect, the program-memory interaction is considered as a possible "threshold concept" [31, 33] . Based on constructivism [16, 23, 41, 42] , the PWS is

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... discussed as a potential beginner's viable model, which can be, later on, refined to what Ben-Ari describes as a viable computer model [5] . The extent to which the PWS can be used as a conceptual framework, which will enable teachers and learners to focus on program-memory interaction across a variety of dimensions, and eventually relate them to form a coherent whole, is also examined. The exact implementation of the PWS in the context of the various programming languages is beyond the scope of this paper. Nevertheless, it constitutes a topic for detailed study and future research.