Lesson 12: Decomposition and Design

Computer science is all about problem-solving. Solving problems is a core component of a software engineer's work, and we have learned about ways to create and improve solutions in The Neighborhood. Let's consider how we solve problems in our daily lives.

Group: Place students in groups of three or four.

Do This: Have students work with their groups to write an algorithm for the scenario.

Discuss: What process did you take to decide on your algorithm?

Discussion Goal: Students share the approaches they took to develop their algorithm. Students discuss how they broke the problem down into smaller tasks, such as sorting the colors into piles and then counting the number of M&M's in each pile.

Sometimes, problems are so big that we need to break them down into manageable tasks first. This process is called decomposition, and we will learn how to use this approach to break down problems.

Do This: Review the lesson objectives.

Do This: Define decomposition.

Revisit the scenario from the warm up or an example of a personal interest or daily activity. Briefly discuss how the scenario would be broken down into specific tasks or steps.

Do This: Explain the steps to solving a programming problem.

• Understand
• Expected Behavior
• Supporting Information
• Mapping
• Assemble
• Testing

As you work through these problems, use decomposition strategies to break them down into manageable tasks. Consider any edge cases for your solutions and review your solutions for any redundancy.

Group: Place students in pairs.

Distribute: Give each pair a copy of the Decomposition handout.

Do This: Direct students to work with their partners to write pseudocode for one of the choice problems on the Decomposition handout and add their new method to the PainterPlus UML diagram.

Do This: Direct students to Level 3 on Code Studio to complete a choice level to implement their new method.

When software engineers develop solutions, they try to account for potential errors and different ways a user might use the program. However, they have to be careful about being redundant to keep their programs efficient.

Do This: Define edge case and redundant code.

This is a good time to commit our code and save our new version of the PainterPlus class to the Backpack. Anytime we make changes to our programs, it is helpful to commit, or save, our work as a new version in case we need to revert to a previous version.

Do This: Play the music clip to cue committing their code and saving the new version of the PainterPlus class to the Backpack.

When we write new code, getting feedback from our peers is helpful to make sure we have met the requirements of the problem efficiently.

Do This: Click through the animated slide to have students participate in the Code Review Call and Response.

Do This: Direct students to complete a code review on their chosen problem on Level 2.

Conducting code reviews on choice levels is slightly different than on single levels. To conduct a code review on a choice level:

1. Students select the level they completed to request a code review on their work.
2. Students return to the options by clicking the bubble at the top of the page.
3. Students select the level their peer completed to give feedback on their work.

To review the feedback given on their work, students return to the options by clicking the bubble at the top of the page, then select the level they completed.

You have made a lot of progress developing your software engineering skills. Let's take a moment to reflect on our progress and growth.

Do This: Direct students to use the sentence starters on the Unit 1 Guide to reflect on their progress and growth as software engineers.

Do This: Review the concepts covered in this lesson.

Display: Key Vocabulary

Check For Understanding Question(s) and solutions can be found in each lesson on Code Studio. You can use these questions as an exit ticket.