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involve VPS). 17<br />

• The teacher uses UUhistle (or a similar system) in class in program animation mode to explore<br />

how example programs work. The visualization serves as an illustration of useful examples. The<br />

examples are carefully chosen so that the programs are difficult to understand while their execution<br />

is hidden but easier when it is explicit. VPS might also be used in class so that students vote on<br />

key steps, and incorrect answers are also explored and explained (cf. Pears and Rogalli, 2011).<br />

• Example selection draws on misconception catalogues so that the example programs encourage<br />

students to experience fruitful cognitive conflict and detect their misconceptions. When possible,<br />

teachers engage students in conversation about the mistakes they make during VPS. Teachers can<br />

explicitly warn about common misconceptions in class, and use the visualization to demonstrate<br />

their non-viability.<br />

• Students encounter example programs that work in mysterious or unexpected ways that cannot<br />

be explained without a better understanding of related concepts (e.g., references, parameters).<br />

UUhistle is then used to figure out why the program works as it does.<br />

• As a special case of the above, UUhistle is used to find a bug in an example program, which can<br />

then be fixed.<br />

• Students use (the full build of) UUhistle to visually debug their own programs.<br />

• VPS exercises are explicitly referred to in other assignments. This can take many forms. For instance,<br />

a program-writing assignment may refer to an earlier VPS exercise as a necessary prerequisite, or<br />

a VPS exercise may be embedded into a larger assignment, or it may be mentioned as a potential<br />

learning aid to be used in case the student has trouble with a program-writing task. Crucially, the<br />

purpose and goals of the VPS exercise in relation to the other assignment are made clear so that<br />

students know why they are doing the specific exercise.<br />

• Visualization-based assignments feature ‘planlike’ example programs that have explicit high-level<br />

goals.<br />

Encountering just one or a few early cases where a concrete benefit is gained from understanding the<br />

visualization may greatly affect students’ perceptions of the VPS system, and motivate them to adopt a<br />

deeper approach as they work on future VPS exercises.<br />

17.6.3 We have already incorporated some of our advice into UUhistle<br />

Some of our recommendations on teaching about VPS can be incorporated into a software tool such as<br />

UUhistle. We have already begun work on some of them. As soon as the first drafts of our outcome<br />

space emerged, we reprioritized the items in UUhistle’s feature requests list, and added to it, on the<br />

basis of our results. Broadly speaking, we switched priorities from seeking greater coverage of language<br />

features and other technical improvements towards features that encourage students to seek meaning in<br />

the visualization and enable them to genuinely benefit from the tool. The main differences between the<br />

prototype that the students in this study used and the current version of UUhistle from Chapter 13 were<br />

outlined in Section 16.4.2. The following recent features were partially inspired by the results we have<br />

presented in this chapter:<br />

• the Info box and its associated explanatory texts, which seek to draw the learner’s attention to the<br />

conceptual content of the visualization and invite exploration of programming concepts;<br />

17 We may reflect on the suggestions listed here against the context of the CS1–Imp–Pyth course that we studied. In that<br />

course offering, there was some use of UUhistle’s visualization in lectures, but for the most part, the integration of UUhistle<br />

and VPS with other aspects of the course was limited (see Section 16.4). In effect, it was largely left to the students to<br />

perceive meaning in the visualization and to relate it to other assignments and programming in general.<br />

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