Problem-Solving Strategies - Guide to Teaching Computer Science: An Activity-Based Approach - page 78

mended that each pair will work both on the problems it developed and on
the problems developed by at least one more pair. In this way, each student
examines four problems. The problem exchange between the pairs also
contributes to the discussion that takes place in Stage B.
• Stage B: Discussion between pairs
Each two pairs that exchanged their problems discuss together each of the
four problems. In this discussion, they are asked to:
a. Compare their solutions
b. List guidelines for a teacher who evaluates learners' investigation of
the variables needed for solving a given problem
• Stage C: Presentations and discussion in the course plenum
If time allows, a discussion can be facilitated in the course plenum in
which the teacher guidelines, formulated by all groups, are examined.
Activities 33-34 focus on roles of variables, which is a recently introduced ap-
proach that can be utilized in teaching programming to novice learners.
The role of a variable is defined according to the dynamic character of the vari-
able, embodied by the succession of values that variable gets, and how the new
values assigned to the variable relate to other variables. For example, in the role of
a stepper , a variable is assigned a succession of values known in advance as soon
as the succession starts. The role concept, however, is not concerned with how a
variable is used in the program; a stepper is a stepper whether it is used to index
elements in an array or to count the number of input values (Ben-Ari and Sajaniemi
2003 ; Sajaniemi 2005 ).
The concept of roles of variables is concerned with the deep structure of the pro-
gram. The name of the variable, its place within an expression, relations between
expressions and assignments, and the control statements, are important factors in
role assignment; the surface structure of the program, primarily its syntactic struc-
ture, is less relevant to the role concept.
Activities 33 and 34 focus on the roles of variables. They can be facilitated in the
MTCS course, either in the class or as homework assignments.
Activity 33: Roles of Variables—Discovery Learning and Reflection
The students are directed to the Web site of roles of variables, 3 to learn the
relevant concepts and practice them by themselves. Then, the students are
asked to reflect on their experience.
3 The roles of variables home page (http://www.cs.joensuu.fi/~saja/var_roles/ very rich and con-
tains different kinds of educational resources).