Programming Fundamentals/Loops/While Loops

A while loop is a control flow statement that allows code to be executed repeatedly based on a given Boolean condition. The while loop can be thought of as a repeating if statement. This activity introduces while loops. This activity will help you understand how to use while loops in a program.

Objectives

• Understand while loop concepts.
• Understand how while loops are specified in a program.
• Single-step through a program to observe while loop execution.

Prerequisites

Learners should already be familiar with conditions.

Introduction

Flowgorithm while loop

Review the flowchart example on the right.

Questions

• What flowcharting symbol is used to indicate a while loop?
• How are while loops structured?

Activity

With a partner, perform the following:

1. Using a visual programming language, create a program similar to the flowchart on the right based on the following steps.
2. Start by creating a while loop that counts from 1 to 5 by 1.
3. Save the program.
4. Test the program to verify that it works correctly.
5. Modify the program to count from 1 to 10 by 1.
6. Modify the program to count from 5 to 10 by 1.
7. Modify the program to count from 0 to 10 by 2.
8. Trade places, so that both partners have an opportunity to "drive" the visual programming environment.
9. Modify the program to count from any start value the user enters to 10 by 1.
10. Modify the program to count from any start value the user enters to any stop value the user enters by 1.
11. Modify the program to count from any start value the user enters to any stop value the user enters by any increment value the user enters.
12. Change the environment to use a slow run speed and/or step through the program one shape at a time.
13. Working together, create a list of changes that might be made to use while loops in programs you've already written. What parts could be repeated and how would the loop terminate?

Applications

• Identify specific steps which must be followed when creating a program using while loops.
• Discuss your activity experience with your classmates. What surprised you? What have you learned that you can apply to your own school or work environment?