This article continues with the curriculum redeft- nition effort and focuses on concepts that should be taught in an introductory programming course. Textbooks used in introductory programming courses typically focus on the syntax and semantics of constructs in a language. New research with novice programmers, however, suggests that language This work was sponsored by the National Science Foundation, under NSF Grants MDR-8470150, DPE-8470014, and IST-8505019

Claims have been proposed as a means of expressing HCI knowledge that is associated with a specific artefact and usage context. Claims describe design trade-offs and record HCI knowledge related to a specific design, or artefact, as psychological design rationale. Claims are created in the task-artefact cycle of interactive design and evaluation. Usability evaluation establishes a claim for a specific usage context, but this can restrict subsequent reuse of claims related knowledge. To widen the scope of reuse the knowledge contained within claims and their associated artefacts has to be classified and generalized. To address this problem a schema and method for classifying claims is introduced. The schema elaborates the description of HCI knowledge in claims and enables reuse by describing the assumptions and dependencies upon which a claim rests. Methods for generalising claims and discovering new claims from existing claims and artefacts were investigated. A factoring method for evolving child claims from parent claims and their usage scenarios is described. This employs a walkthrough technique based on Norman’s model of action with questions directed at the contributions a claim makes to usability at different stages in interaction. Factoring promotes evolution of child claims that either address different aspects of task support in the same domain as the parent claim, or development of more general child claims for user interface design. The relationships between claims are represented in maps to illustrate histories of task-artefact investigation that lead to claims evolution either via the factoring process or by empirical investigation. The schema and method for claims evolution are illustrated by case studies of claims development in tutoring systems and claims for functional requirements for specification reuse support tools. The paper concludes with a discussion of the contribution that reusable claims can make as a repository of HCI knowledge. 1 1.

: This research is about the problem solving activities of novice programmers as they learn to create recursive LISP programs. Their problem solving not only includes the issue of mental models, but also how to use these mental models in conjunction with other problem solving techniques. In fact, at various stages of their learning, learners seem to use different packages of problem solving methods. Each of these packages we call a mental method. In this paper, we discuss the PETAL learning environment which assists learners in the use of three of these mental methods: the syntactic method, the analytic method and the analysis/synthesis method. PETAL externalizes each mental method through its own customized interface, called a programming environment tool (PET). Such externalization helps learners internalize concepts, and organize relevant knowledge and generally leads to improved learning. The PETAL System itself is presented. Next we discuss a study where one group of students used...