Informatics in Education

The notion of algorithm may be perceived in different levels of abstraction. In the lower levels it is an operational set of instructions. In higher levels it may be viewed as an object with properties, solving a problem with characteristics. Novices mostly relate to the lower levels. Yet, higher levels are very relevant for them as well. We unfold the importance of higher level abstractions for novices, by demonstrating the role of declarative observations of algorithmic problems, and the benefit of developing awareness of such observations in algorithmic problem solving. This is shown in a two-stage study, which first reveals the unfortunate lack of declarative observations, and then displays comparative results of experimental and control groups, which stems from different awareness and competence with declarative observations.

In many occasions, the text describing an algorithmic task may entail a rather intuitive, operational solution scheme. Yet, such a scheme may not necessarily be efficient or correct. Nevertheless, novices demonstrate tendencies to hastily design their solutions that way, and avoid seeking insightful patterns, which may yield better solutions. In this paper, we name and shed light on this theme, and illustrate the essential importance of elaborating insightful patterns, which one may assimilate as general problem solving notions.

Every repetitive process encapsulates a regularity pattern, which may be expressed as an invariant assertion. Invariants embody implicit, insightful properties that characterize the execution of programming statements. Due to their implicit nature, invariants may be less apparent to algorithmic problem solvers. Yet, invariants are essential for designing correct and efficient algorithms. This paper illustrates the essential role of invariants, and examines whether novices tend to look for invariant properties during their algorithmic problem solving. The paper presents a study in which two novel algorithmic challenges were displayed to a group of motivated, novice students. Student solutions to these challenges demonstrate an operational reasoning approach, which does not capture the essence of the problems at hand, and yields non-satisfying results. Some solutions were incorrect, others were inefficient, and some had no convincing justification. These results, and the correct and efficient solutions to both challenges illuminate the importance of assertional reasoning and the fundamental role of invariants.