Find the Entry Points



Updated August 7, 2023

First things first—figure out where the program starts. To execute a program, the loader (typically an operating system) will pass control of the process to a program’s entry point, which begins the run-time execution of the application.

The entry point is the place where a program begins, and it’s important to know what the program is doing once it begins executing the code. When you follow a program from the entry point, you’ll be able to follow the application as it boots up and configures itself to do whatever work it was designed to do.

Some programming languages may enforce conventions for how or where a program should start, while others may give more freedom in how a program is executed.

  • C-family languages, such as C, C++, and Rust, and JVM languages such as Java contain a predefined function called main.

  • Interpreted languages like JavaScript, Python, Ruby, and PHP will simply begin execution at the first statement.

Once your program has control of the process and has begun execution, it will be able to access command-line arguments and environment variables that can be used to dynamically configure the behavior of your application during run time. The program may contain specific logic to check for these arguments or environment variables in order to change the run-time behavior of the application without needing to recompile or redeploy the application.

It’s important to know where and how your program starts because that may give you valuable information as to how the program is configured, which could affect how the program behaves. If you don’t know what run-time configurations your program is using, you may not fully understand what it’s doing, so this is always a good first step.

Leverage Your IDE

Your integrated development environment (IDE) is one of the most important tools you will use when reading code. Your IDE gives you a set of tools to analyze and manipulate your codebase, so choosing a good IDE will help you navigate the code efficiently.

When reading code, you’ll want an IDE that lets you jump to a function definition. This feature is crucial for learning and studying a new codebase, and most modern development environments should support this functionality. This allows you to jump through the codebase to see where a function is defined, which is useful whenever you come across a function call you’re not familiar with.

This feature gives you the ability to step through the codebase and follow the execution path, which helps you build a mental model of the code and what it’s doing. It’s a great way to explore unfamiliar code and can help you get up to speed quickly.

You’re reading a preview of an online book. Buy it now for lifetime access to expert knowledge, including future updates.
If you found this post worthwhile, please share!