The end users are able to operate at the _______ tier.

In three-tier client-server architecture, an application is split into three separate layers: the presentation tier, the application (logic) tier, and the data tier. Each layer has a distinct role and only ever talks to the layer directly above or below it.

The presentation tier is the layer that end users see and interact with directly, it is made up of the screens, forms, buttons and menus that display information and collect input. Since ordinary users never see or touch the underlying business rules or the database, they operate entirely within this presentation layer, entering data and viewing results through it.

The application tier processes business logic behind the scenes, and the data tier stores and retrieves data, but neither is directly accessible to the end user, they are reached only through requests passed on from the presentation tier.

Exam tip: when a question asks which tier the user interacts with, think of it as "the layer you can see on the screen", that is always the presentation tier.