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Abstraction is a major concept in computer science and serves as a powerful tool in software development. Pattern-oriented instruction (POI) is a pedagogical approach that incorporates patterns in an introductory computer science course in order to structure the learning of algorithmic problem solving. This paper examines abstraction processes in the course of solving an algorithmic problem and highlights three distinct, although interrelated, facets of abstraction: pattern recognition, black-boxing, and structure identification. A study that examined the influence of the POI approach on students' abstraction skills is described; students who learned according to the POI approach were compared with students who learned in a traditional manner with regard to analogical reasoning and problem decomposition and solution, as well as verbal expression. The three facets of abstraction were used to analyze students' abstraction skills and their competency in algorithmic problem solving. (Contains 4 figures and 5 tables.)

The rapid evolvement of the computing domain has posed challenges in attempting to bridge the gap between school and the contemporary world of computing, which is related to content, learning culture, and professional norms. We believe that the interaction of high-school students who major in computer science or software engineering with leading representatives of the computing community of practice may motivate them to pursue their studies further or pursue a career in the field. Accordingly, our program aims at exposing talented high-school students "directly by leading experts" to state-of-the-art computing research, advanced technologies, software engineering methodologies, and professional norms. The interaction between the students and the experts, who actually become role models for the students, occurs at two levels: (a) during enrichment plenary meetings, and (b) through one-to-one interaction in which students develop software projects under the apprenticeship-based supervision of professionals from the computing community of practice. In the last four years, six hundred students participated in enrichment activities; 86 of these students accomplished high-level software projects under the supervision of experts. A long-term formative evaluation of the program has been conducted regarding: (1) students' attitudes towards the "different-from-school" style of learning that characterizes the program, and (2) students' performance in developing projects. In this paper, we specifically discuss the contribution of resources that students used for various phases of the project development activity. We found that the following categories of resources were employed by the students: self-learning, mentors, bibliographic resources (the Web, professional articles, professional books), school resources (a school teacher, school learning, and materials), and other human resources (i.e., a classmate the student 's age, a family member, a grown-up acquaintance). Importantly, the findings indicated that during the entire development process the students exhibited self-efficacy, since they relied more on themselves than on other resources. Interestingly, during the entire development process, the web was perceived as the most significant bibliographic resource. Specifically, regarding the need to achieve adequate acquaintance with the theoretical knowledge that was required, self-studying and the web were perceived as the most significant resources, which may imply that the mentors' guidance inspired the students' self-inquiry and self-study. However, during the problem-solving activities, students relied more on the mentors than on bibliographic resources. Based on the study findings, we concluded that professional experts who supervise students in project development may motivate them to acquire in-depth knowledge in computing, promote creativity, as well as enhance self-learning and inquiry ability. In addition, the interaction with role models may contribute to establishing professional norms. We hope that further implementation of the program, along with recruitment of more representative experts from academia and hi-tech industry, will promote a culture of learning and work befitting the dynamic world of industrial computing, thus providing the students with an entry point into the computing community of practice. (Contains 4 figures and 6 tables.)

The computer science high-school teaching community of practice possesses a rich collection of distributed practical knowledge consisting of individual teachers' expertise regarding pedagogy. However, without a proper means of communication and rules of discourse, the individual pieces of knowledge might not be transferred properly within the community, and eventually might get lost. Only when fertile professional communication lines have been established, can the growth of common shared, reusable knowledge bases be reinforced and nurtured. Pedagogical patterns are intended to capture the expert knowledge of the practice of teaching and to transfer that knowledge to other practitioners. This paper discusses how the culture of patterns can be employed to transfer pedagogical knowledge, and thus reinforce peer-communication and collaboration within the computer science high-school teaching community of practice. (Contains 1 table.)

Recursion is a central concept in computer science, yet it is difficult for beginners to comprehend. Israeli high-school students learn recursion in the framework of a special modular program in computer science (Gal-Ezer & Harel, 1999). Some of them are introduced to the concept of recursion in two different paradigms: the procedural programming paradigm and the logic programming (LP) paradigm. Here we discuss the implication of first learning recursion in LP on the students' understanding of the concept. The declarative approach for teaching recursion in logic programming seems to enhance students' recursion comprehension. We found that students who learned recursion in LP before learning it in a procedural paradigm differed, in terms of their mental models of recursion, from those who were acquainted with recursion in procedural programming only. More of the LP students possessed an adequate model of recursion as a process than did the non-LP students. Moreover, the LP students also attained a unique conception of recursion as a tool for knowledge representation. (Contains 3 tables and 1 figure.)

Describes an instructional model for teaching abstract data types (ADTs) to high school students. Presents research results regarding students' conceptualizations of ADTs and their strategies of using them in computer science problem solving. To implement the ADTs, "black boxes" were used. (AEF)