Fundamentals of Software Engineering

Chapter 2. Reading Code

Code is read much more often than it is written.

Guido van Rossum, creator of Python

Despite the way coding is taught, software engineers spend far more time reading code than writing it. In most beginner coding courses, you jump immediately into writing code, focusing on core language concepts and idioms without acknowledging that you’d never learn Polish or Portuguese in a similar manner. And while most academic projects start from a blank slate, practicing developers are almost always working within the confines of code that has taken years to arrive at its current state, something you can explore in depth in Chapter 6.

With the advent of agentic or chat-oriented programming,¹ reading code will become even more important for software engineers. While it may not be your first choice, you will work with code you did not write. Take heart, there are techniques to help you orient yourself when you encounter unfamiliar code. This chapter will go over why reading code can be challenging, and we’ll give some tips to make the process simpler.

The Challenge of Working with Existing Code

Regardless of how you learned to code, you probably spent much of your time in the blissful space known as greenfield development, where you experience the job of starting from scratch, unencumbered by the baggage of prior work. Yet, in your professional life, you’ve likely had vanishingly few opportunities to build an application from a blank editor. As a practicing software ...