ANS(C)
Reasons for Maintainence:
Corrective Reasons:
Maintenance has to be performed to repair the existing faults in the software. This might include bug fixes due to a bad code, or a major system repair if the problem is advanced. Bugs may also appear in case of change in the hardware, OS or other accompanying parts in the system. Maintenance involves testing to detect a problem and injecting a fix without disturbing the rest of the system.
Adaptive Reasons:
As we mentioned above, a software ecosystem is continuously changing, and regular maintenance is required to help it adapt to the new changes. Work patterns, software platforms, compilers, hardware upgrades, etc. all affect the working of software. In essence, adaptive maintenance is required to keep your software fresh in changing circumstances and increasing the lifespan of the software.
Perfective Reasons:
One can also undergo the software maintenance process to fine tune the performance ability, functionality and usability of the software. It can simply range from changing the GUI of the software to make it more attractive and user friendly to making drastic changes in the core code to improve the runtime and performance. One can keep building up on the initial work done to make the software perfectly adaptive in the changing circumstances. Perfective maintenance accounts for around 60% of the maintenance cost.
Preventive Reasons:
Preventive maintenance is essentially a pre-emptive strike against problems. By carefully observing the conditions in the ecosystem, an expert can take decisions to re-engineer the software through data and code restructuring. This type of maintenance does not really contribute to the functionality of the software, but rather acts like a vaccine to prevent problems and the additional repair costs that come with them.
Legal and Business Reasons:
It is not just the technological parameters that change with time, but also the legal and business side of things. Adaptiveness is required not only to stay on par with your competition, but to be on par with the latest legal norms and requirements related to privacy and security of the users. Business patterns and government rules are also subject to constant change and improvement.
SOURCE: https://www.optimusinfo.com/blog/5-reasons-why-software-maintenance-is-a-must
