Question

Legacy code: how to work with obsolete or unknown code

Answer 1

Definition of the legacy code
What are the disadvantages of the legacy code?
Refactoring: the proper answer to legacy code

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Legacy code: how to work with obsolete or unknown code

Source code is the heart of software . The proper operation of the program and the availability of its functions depend on the instructions and commands stated in the code. Programmers edit, maintain and update this code regularly to provide users with the best usability possible . Changes to the code can cause software errors or compromise a program's ability to run..

It is always problematic for developers and programmers to maintain and update software with code that they did not write themselves or that was written for obsolete operating systems or with outdated versions of the programming language. Here we tell you what exactly the legacy code is and the best ways to work with it.

Index

1. Definition of the legacy code
2. What are the disadvantages of the legacy code?
3. Refactoring: the proper answer to legacy code

Definition of the legacy code

The term legacy code is used in software engineering to refer to code that has become obsolete and is generally no longer actively developed . The legacy code can be defined, in a way, as the opposite of the clean code, easy to understand intuitively, to maintain and to adapt. The legacy code is inefficient, outdated, and chaotic, which can cause a multitude of problems . The exact meaning of the term largely depends on the developer's point of view and the particular situation. In principle, however, the legacy code is characterized by the following aspects:

• The original developer no longer maintains the code.
• The code was originally written for operating systems that are no longer supported.
• You cannot perform automatic tests for errors

What are the disadvantages of the legacy code?

Why is the legacy code used if it has so many drawbacks ? Simply because it is unavoidable: often, during a project, a new programmer takes over the maintenance and development of the code. While the original developer of the code could understand it intuitively in most cases, new members of the team have to struggle to figure out what it does. In that case, parts of the code may not be readable or understood correctly..

When code is maintained, improved, and edited by many different programmers over many years, it can become a very difficult mosaic to understand and modify. At some point in its history, the code and its effects become incomprehensible, making it impossible to update or correct them properly.

Another drawback of legacy code is that it does not allow for regression testing or automated testing due to its patchy, inefficient, and unwieldy nature. As a result, developers dealing with legacy code have to spend a lot more effort doing manual testing , which makes bugs harder to fix and updates more difficult to implement..

Refactoring: the proper answer to legacy code

Developers have various reasons for being reluctant to deal with the legacy code . One of the main problems is the fact that they cannot automatically test it for errors or bugs. So what can developers do if they have to deal with legacy code in the course of a new project?

The most appropriate solution is probably refactoring or restructuring. With this development strategy, the code is restructured without changing its original function. However, before the actual restructuring can be done, developers must first understand what each code component does. In addition, they must test all functions in order to validate them.

Only after you understand how the code works can you do the actual refactoring . The code is optimized piece by piece. Thus, redundant lines of code are rewritten or eliminated, classes and variables are simplified and merged, command methods are adapted and rewritten. Ultimately, the refactoring is a general overhaul of the legacy code . The result is code that is easier to understand and maintain, and faster to adapt.

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