Assessment Tool

Lecture 9: Iteration

Content Tested: While and For Loops

Lecture Content:

Iteration
Loops and Nested Loops
While statements
For statements

Goals:

Ability to synthesize and integrate information
Learn concepts and theories
Develop capacity to think for oneself
Develop ability to think creatively
Ability to formalize an explanation

Assessment Technique: Discussion Questions

Purpose:

These questions give students a way to think about for and while loops at a higher level.

Activity:

We saw in today's lecture the introduction of loops, specifically the "for" and the "while" loops. In your group, please discuss the following questions.

1. Can every while loop be re-written as a for loop? If yes, please describe how you would convert a generic while loop into a for loop. If no, give an example of a while loop that cannot be re-written as a for loop.

2. Can every for loop be re-written as a while loop? (Hint: recall today's lecture) If yes, please describe how you would convert a generic for loop into a while loop. If no, give an example of a for loop that cannot be re-written as a while loop.

3. Let's define a new language called C-. C- is the C language with no for loops. Do C and C- have the same expressive power? (Expressive power means that if you can write a program in C then you can write a program in C- and if you can write a program in C- you can write a program in C.) Why or why not?

Possible Solutions

1. Yes, every while loop can be re-written as a for loop.

while (condition) {
statement;
}

can be re-written as:

for ( ; condition; ) {
statement;
}

(The instructor might need to help the students with this since having an empty initialization and an empty update might confuse the students.)

2. Yes, every for loop can be re-written as a while loop.

for (initialization; condition; update) {
statement;
}

can be re-written as:

initialization;
while (condition) {
statement;
update;
}

3. Yes, C and C- have the same expressive power. We just showed that every for loop can be re-written as a while loop, so this is how one would convert a C program to a C- program. A C- program is a valid C program since C- is a subset of the C language.

Possible Uses of Activity:

Have students work in groups and present their findings to the rest of the class. Before having a group discuss their answers, poll the groups to see what answers they have to each question. This activity should serve as a great discussion starter.