Teaching Planning - Guide to Teaching Computer Science: An Activity-Based Approach - page 208

− Learners understand that each array cell functions like a variable.
− Learners distinguish between the expressions a1 —a single variable, a [1]—
the value of the array cell whose index is 1, and a [ i ]—the value of an array
cell whose index is i —the value of a variable i .
− Learners distinguish between the expression i as an index and a [ i ] as a cell
content.
− Learners know how to scan an array.
4. The following activities to be facilitated in the lesson were designed according to
the following guidelines:
− The lesson addresses arrays from two perspectives: conceptual and practical.
It is important to illuminate these two perspectives to the pupils.
− The lesson involves different kinds of activities: a trigger, work in pairs, a
class discussion, and a lab activity.
− The lesson plan takes into the consideration the expected difficulties men-
tioned in Sect. 11.3.1 and attempts to reduce the level of abstraction (when
needed) to help learners overcome these difficulties.
The lesson activities are presented in what follows along the lesson time line
together with their main idea. In some cases, we also specify the assignment.
− Presentation of a trigger to the class plenum: The learners are asked to solve
a problem whose solution requests an array and then, in pairs, to check the
pair's solution. Since at this stage, they are not familiar with the concept of
array, they cannot solve the problem and therefore, it is expected that they will
feel some inconvenience.
An example of such a trigger is: Write a program that prints the number of
pupils whose grade is bigger than the class average for a class of 34 high
school pupils.
One solution that pupils may suggest is to read the grades twice: first, in
order to calculate the average, and second, in order to count the number of
grades which are bigger than the average. In this case, a common computer
science convention should be added to the question formulation: In comput-
erized systems, it is common to enter data only once. The learners will be
given additional time to deal with the new constraint, and to realize that it is
not possible to solve the problem with this restriction.
Another solution that can be suggested by the pupils is to define 34 dif-
ferent variables, one for each grade, namely, a1, a2, …, a34 . In this case, the
learners should be directed to observe what this solution includes 34 input
statements, 34 addition statements and 34 condition statements. In this case,
additional common computer science convention can be added: Computer-
ized systems should be able to generalize the problem; in this case, what will
we do if there are 100 learners? After all, we wish the computer to work for
us and not us to work for the computer. As in the previous case, the learners
will get extra time to deal with the new constraint, and again, to realize that it
is not possible to solve the problem with this restriction.