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Introductory programming courses (CS1) are difficult for novices. Inspired by "Problem solving followed by instruction" and "Productive Failure" approaches, we define an original "necessity-driven" learning design. Students are put in an apparently well-known situation, but this time they miss an essential ingredient (the target concept) to solve the problem. Then, struggling to solve it, they experience the necessity of that concept. A direct instruction phase follows. Finally, students return to the problem with the necessary knowledge to solve it. In a typical CS1 learning path, we recognise a challenging "rollercoaster of abstraction". We provide examples of learning sequences designed with our approach to support students when the abstraction changes (both upward and downward) inside the programming language, for example, when a new construct (and the related syntactical, conceptual, and strategic knowledge) is introduced. Also, we discuss the benefits of our design in light of Informatics education literature.

The pervasiveness of Computer Science (CS) in today's digital society and the extensive use of computational methods in other sciences call for its introduction in the school curriculum. Hence, Computer Science Education is becoming more and more relevant. In CS K-12 education, computational thinking (CT) is one of the abused buzzwords: different stakeholders (media, educators, politicians) give it different meanings, some more oriented to CS, others more linked to its interdisciplinary value. The expression was introduced by two leading researchers, Jeannette Wing (in 2006) and Seymour Papert (much early, in 1980), each of them stressing different aspects of a common theme. This paper will use a historical approach to review, discuss, and put in context these first two educational and epistemological approaches to CT. We will relate them to today's context and evaluate what aspects are still relevant for CS K-12 education. Of the two, particular interest is devoted to "Papert's CT," which is the lesser-known and the lesser-studied. We will conclude that "Wing's CT" and "Papert's CT," when correctly understood, are both relevant to today's computer science education. From Wing, we should retain computer science's centrality, CT being the (scientific and cultural) substratum of the technical competencies. Under this interpretation, CT is a lens and a set of categories for understanding the algorithmic fabric of today's world. From Papert, we should retain the constructionist idea that only a social and affective involvement of students into the technical content will make programming an interdisciplinary tool for learning (also) other disciplines. We will also discuss the often quoted (and often unverified) claim that CT automatically "transfers" to other broad 21st century skills. Our analysis will be relevant for educators and scholars to recognize and avoid misconceptions and build on the two core roots of CT.

In this paper, we present an activity to introduce the idea of public-key cryptography and to make pre-service STEM teachers explore fundamental informatics and mathematical concepts and methods. We follow the Theory of Didactical Situations within the Didactical Engineering methodology (both widely used in mathematics education research) to design and analyse a didactical situation about asymmetric cryptography using graphs. Following the phases of Didactical Engineering, after the preliminary analysis of the content, the constraints and conditions of the teaching context, we conceived and analysed the situation a priori, with a particular focus on the milieu (the set of elements students can interact with) and on the choices for the didactical variables. We discuss their impact on the problem-solving strategies the participants need to elaborate to decrypt an encrypted message. We implemented our situation and collected qualitative data. We then analysed a posteriori the different strategies that participants used. The comparison of the a posteriori analysis with the a priori analysis showed the learning potential of the activity. To elaborate on different problem-solving strategies, the participants need to explore and understand several concepts and methods from mathematics, informatics, and the frontier of the two disciplines, also moving between different semiotic registers. [ABSTRACT FROM AUTHOR]

Introductory programming courses (CS1) are difficult for novices. Inspired by Problem solving followed by instruction and Productive Failure approaches, we define an original "necessity-driven" learning design. Students are put in an apparently well-known situation, but this time they miss an essential ingredient (the target concept) to solve the problem. Then, struggling to solve it, they experience the necessity of that concept. A direct instruction phase follows. Finally, students return to the problem with the necessary knowledge to solve it. In a typical CS1 learning path, we recognise a challenging "rollercoaster of abstraction". We provide examples of learning sequences designed with our approach to support students when the abstraction changes (both upward and downward) inside the programming language, for example, when a new construct (and the related syntactical, conceptual, and strategic knowledge) is introduced. Also, we discuss the benefits of our design in light of Informatics education literature. [ABSTRACT FROM AUTHOR]

> Context * The meaning and implications of "computational thinking" (CT) are only now starting to be clarified, and the applications of the Computer Science (CS) Unplugged approach are becoming clearer as research is appearing. Now is a good time to consider how these relate, and what the opportunities and issues are for teachers using this approach. > Problem * The goal here is to connect computational thinking explicitly to the CS Unplugged pedagogical approach, and to identify the context where Unplugged can be used effectively. > Method * We take a theoretical approach, selecting a representative sample of CS Unplugged activities and mapping them to CT concepts. > Results * The CS Unplugged activities map well onto commonly accepted CT concepts, although caution must be taken not to regard CS Unplugged as being a complete approach to CT education. > Implications * There is evidence that CS Unplugged activities have a useful role to help students and teachers engage with CT, and to support hands-on activities with digital devices. > Constructivist content * A constructivist approach to teaching computer science concepts can be particularly valuable at present because the public (and many teachers who are likely to have to become engaged with the subject) do not see CS as something they are likely to understand. Providing a clear way for anyone to construct this knowledge for themselves gives an opportunity to empower them when it might otherwise have been regarded as a domain that is open to only a select few. [ABSTRACT FROM AUTHOR]

The commentaries provide useful questions and responses that help us understand better how unplugged activities serve as scaffolding to engage students in computer science. They help us to consider how activities relate to computational thinking, particularly by connecting the scaffolding in the activities to the limits of computation. This in turn helps us to navigate the somewhat disputed boundary between activities that clearly use computation as it occurs on physical devices, and metaphors that could potentially be misleading. [ABSTRACT FROM AUTHOR]