How to best handle legacy code

The heart of a piece of software is its source code. Whether the program works the way it is supposed to and which functions can be performed depends on instructions and commands contained in this code. Programmers regularly edit, maintain, and update this code to optimize its usability. Any changes made to the code may result in software errors or affect the program’s functionality.

Maintaining and updating software is always particularly problematic for developers and programmers when they have to work with code that they did not write themselves or that was written for older operating systems that are no longer supported in equally old versions of the underlying programming language. Here you will learn exactly what legacy code is and how to best handle it.

The term “legacy code” is used in the field of software technology. This term refers to old code that is usually no longer in active development. In a sense, legacy code is the antithesis of clean code which is easy to understand, maintain, and adapt. Legacy code is unwieldy, outdated, and messy, which can lead to numerous problems. The exact meaning of the term greatly depends on the developer’s perspective and current situation. However, in general, legacy code is characterized by the following aspects:

• The code is no longer being maintained by the original developer
• The code was originally written for operating systems that are no longer supported
• You cannot use automated tests to find bugs in this code

Why is legacy code used at all if it has so many disadvantages? Well, it simply cannot always be avoided. Often, over the course of a project, a new programmer will take over the maintenance and further development of the code. While the original developer usually has an intuitive understanding of the code, new team members will have to develop that same understanding. Sometimes parts of the code are overlooked or not fully understood.

If a piece of code is maintained, updated, and edited by numerous different programmers over many years, that code can become a patchwork quilt as time goes on that is increasingly difficult to understand and modify. The problem is that, at some point, it will become impossible to make any required updates or modifications to the code as no one will understand it or its functionality.

Another disadvantage of legacy code is that you cannot perform regression testing (automated tests) on it because its programming is too bulky, unwieldy, and patchy. That’s why developers dealing with legacy code have to perform a significantly greater amount of manual testing. It is more difficult to fix bugs and more complicated to implement updates.

Legacy code is something that developers are reluctant to deal with for a variety of reasons. One of the biggest issues is that you cannot use automated tests to check the code for bugs or errors. So, what can developers do if they suddenly find themselves confronted with legacy code when working on a new project?

The best solution is probably refactoring the code. In this development process, code is restructured without changing its original function. However, before the actual restructuring can happen, the programmers must first understand what each part of the code is responsible for. In addition, tests must be performed to check all the functions.

They can only begin the actual refactoring once it is clear how the code works. The code is then optimized piece by piece. Any unnecessary code is removed or rewritten. Classes and variables in the code are simplified and merged. Command methods are adapted and rewritten. In the end, refactoring is basically a general overhaul of the legacy code. The resulting code is easier to understand, maintain, and adapt.