What do we call a piece of executable code added to an existing program to fix identified problems?

A piece of executable code added to an existing program to fix identified problems is called a patch. Patches are used to correct bugs, security vulnerabilities, or other specific issues within a software application. They typically address known problems without changing the overall functionality of the software significantly.

Patches are essential for maintaining software integrity and user security. When an issue is discovered after the original release of software, developers create a patch to resolve that specific bug, which can then be deployed by users to update their systems. This is also an important part of software maintenance, allowing for continuous improvement and enhanced stability.

In contrast, options like upgrade, extension, or enhancement typically refer to broader changes, which could involve new features or functionalities rather than merely fixing existing issues. Upgrades often involve significant changes to the software version, while extensions and enhancements may add new capabilities rather than focus solely on rectifying existing problems.