Welcome to the Legacy Code module. In this module, you’ll be working with existing code rather than starting from scratch. This is a crucial skill for professional developers, as most of your career will involve understanding, maintaining, and extending codebases created by others.

You will need:

• 📓 Notebook and pen
• 💻 VSCode and Chrome Devtools
• 🧩 The PurpleForest application (our Bluesky type app)
• 🔍 Your analytical thinking skills, so get those Logic module notes out

What is Legacy Code?

Legacy code is any existing codebase that you didn’t write. (Or maybe you wrote a long time ago and have forgotten.) It will also likely have limited documentation, bugs, and unusual design decisions. You might have forgotten why it’s like this, but it still needs to be maintained and improved.

Sound challenging? It is! But it’s also where many developers spend most of their working lives. The skills you’ll develop in this module will prepare you for the reality of professional software development.

What You’ll Learn

By the end of this module, you will have had the opportunity to:

• Navigate and understand an unfamiliar codebase
• Debug existing features without breaking functionality
• Fix issues using systematic approaches
• Extend legacy applications with new features
• Work effectively within existing architectural constraints

In this module you will start building the mental models you’ll need to become effective at working with legacy code. You will use a lot of models and skills you already have to help you. And let’s also talk a bit about handling the fear of breaking things. We will use logic to conquer fear.