isbn9789526046266

Figure 11.23: A C++ program within VIP. The at method of a string is just about to be called. The
evaluation pane in the top right-hand corner displays previous steps; in this case, the
most recent steps involve the evaluation of at’s parameter expression. This is a teachergiven
example program, into which the teacher has embedded natural language information
about individual lines of code. One such explanatory message is shown in the top left-hand
corner.
course; this does not imply that VIP was responsible for this trend, however.
Lahtinen et al. (2007b) surveyed programming students in a number of European universities on their
opinions of program visualization. This study was not specific to VIP, but roughly half of the students
surveyed had taken a course in which VIP was used. The survey results suggest that the students who
found programming challenging but manageable were the most positive about using visualizations, while
the strongest and weakest students were less impressed. These findings are in line with the study of
Ben-Bassat Levy et al. (2003) on Jeliot 2000, discussed above, in which a ‘middle effect’ was observed.
Ahoniemi and Lahtinen (2007) conducted an experiment in which randomly selected students used
VIP during CS1, while a control group did not. They tested the students on small code-writing tasks. No
significant differences were found when the entire treatment group and control group were considered.
However, Ahoniemi and Lahtinen also identified among their students “novices and strugglers” who either
had no prior programming experience or for whom the course was difficult. Of the novices and strugglers,
the ones who used VIP did significantly better than the ones in the control group. Ahoniemi and Lahtinen
also surveyed the students to find out how much time they had used to review materials and found that
the novices and strugglers in the VIP group used more time than the ones in the control group did; this
is not very surprising, since the students who used VIP had some extra materials (the visualizations and
their usage instructions) to study. The authors conclude that the benefit of visualizations may not be
directly due to the visualization itself but to how the visualization makes studying more interesting and
leads to increased time on task.
Isohanni and Knobelsdorf (2010) qualitatively explored how CS1 students used VIP on their own.
They report that students use VIP for three purposes: exploring code, testing, and debugging. Isohanni
and Knobelsdorf discuss examples of ways in which students use VIP for debugging in particular. Some
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