What is the process called when software is modified post-delivery to correct issues or enhance performance?

The process of modifying software after its delivery to correct issues or enhance performance is referred to as maintenance. Maintenance encompasses various activities that occur after the software has been deployed, including fixing bugs, updating features, optimizing performance, and adapting the software to changes in its operating environment or user requirements.

In the context of software development, maintenance is crucial because it ensures that the software continues to meet users' needs and remains functional over time. This often involves regular updates and patches to address any problems that users encounter or to improve the software's overall quality.

While concepts like refactoring and upgrading may involve changes to the software, they don't encompass the entire scope of activities included in maintenance. Refactoring focuses specifically on restructuring existing code without changing its external behavior to improve its internal structure, and upgrading typically refers to moving to a newer version of software or implementing new features, which may or may not address ongoing issues.