Which of the following describes all components of a system that provide information and controls for the user?

The user interface comprises all components of a system that facilitate interaction between the user and the software. It includes elements such as buttons, menus, and forms that gather user inputs and display information, making it essential for user engagement and experience. The user interface serves as the point of interaction where users can access functionalities and controls, thereby allowing them to perform tasks and receive feedback from the system.

The other options do not encompass the full set of components that provide information and controls for users. A test case is a specific set of conditions and variables under which a tester assesses whether a software application is working as intended but doesn't include user interaction components. Validation refers to the processes that ensure a product meets the requirements and fulfills its intended purpose, which is more about quality assurance than user interaction. Agile methodology describes a framework for software development but does not pertain directly to the components that facilitate user interaction.