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Figure 11.34: An assignment on string catenation within the Online Tutoring System (Kollmansberger,<br />

2010). The student has first chosen the expression txtFirst.Text + txtSecond.Text<br />

for evaluation, then the subexpression txtFirst.Text. Now the system informs them<br />

that the next step is to access the variable: consequently the user has to look at the values<br />

in memory (on the right) and type in "11" (in quotes, to highlight that it is a string).<br />

Subsequent steps include typing in "4" and "114" at the appropriate moments.<br />

Figure 11.35: Stages of expression evaluation within the Online Tutoring System (Kollmansberger, 2010).<br />

Some steps have been omitted.<br />

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