When you first open ZEMAX (either the demo or full, licensed versions), you will see the main menu bar, button bar and Lens Data Editor (LDE).

All of the features that ZEMAX has to offer can be accessed through the various menus in the main menu bar. Shortcuts to most of these features are available for convenience in the button bar below the main menu bar. The assigned buttons can be changed via the menu option, "File > Preferences".

Beneath the button bar is the Lens Data Editor. The window containing the editor can be moved and resized to any convenient location. The Lens Data Editor has columns for Comments, Radius, Thickness, Glass, and Semi-Diameter (radial clear aperture) and Conic constant. The latter five data items are used to define the majority of optical components.

Each row corresponds to an optical surface. Each surface has its own local coordinate system. The position of each surface along the optical axis is referenced to the previous surface. In other words, the “Thickness” column in the Lens Data Editor refers to the distance from the previous surface and not from a global reference point.

By default, there are three surfaces shown: the object, stop, and image. These are denoted by OBJ, STO, and IMA in the small column on the left hand side. The second column also displays a surface type, the default of which is the "Standard" surface. There are many other surface types available. The columns to the right of the Conic constant column are used for setting additional parameters for more advanced surface types.