Dead code is code within a software program that the program cannot reach or does not actually use. It can be present for a wide variety of reasons, and as people work with software, they identify dead code and decide what to do about it. In some cases, people can safely remove it without compromising the program, and may do so to make the program more efficient. Other situations may require people to leave the code in, or to use care when excising it to avoid causing a problem.
One reason to have dead code is the use of routines during debugging without removing those routines later. The program doesn't actually use the code and may in fact be cut off from it, but it lingers in the system. People may also generate dead code by reusing sections from another program, making changes to software, or inserting code with the idea of using it in the future. Depending on the structure of the program, it may execute the code but not do anything with it, or it may find the material completely unreachable.
This segment within a program wastes time and space. It can also interfere with functionality in some cases. The program may find dead code confusing or misleading and generate errors. When people find examples, they must review the program carefully to see how the code interacts with it. It may be necessary to insert new code or modify surrounding material in order to remove the code safely. In other instances, it can be safely taken out.
When dead code consists of material added with future contingencies in mind, it may be left in place. People can access it when and if it is ever needed and activate it so the program can use it. This can be useful for situations like debugging, where having things built into the structure of the program can make it easier to identify and address flaws and other issues. The code may also create a vulnerability, an important consideration when deciding how to handle it.
With each update, software tends to accrue some loose ends and dead code over time. Functions change, people add material, new programmers join and think about coding challenges differently, and detritus builds up. Periodic reviews to check for extraneous or potentially malicious code are an important part of managing the program. People can issue patches or new releases to address the issue and allow users to enjoy a smoother operating experience, as well as improved functionality and safety.