The top left button of the toolbar opens a new Map Display Window. Each map display has a unique set of layers to display and region settings. Other toolbar buttons add layers of different types for display in the selected map display window. There are additional buttons for saving or opening workspace file, and others. Map layers are listed in the window frame below the toolbar. Layers can include raster and vector maps, vector labels, and commands (where any GRASS command can be written). Layers are displayed as arranged in the layer tree: the bottom layer is displayed first and the top layer is displayed last, as if the layers were a series of stacked overlays. The check box to the left of each layer makes it active or inactive for display. Only active layers are displayed/redisplayed when the display button is pressed. Layers can be organized into groups, entire groups can be activated or deactivated for display. Layer tree composition can be saved to a workspace file and opened in subsequent sessions, restoring all layers and their display options. A right mouse click on a layer or left clicking the button to the right of the layer opens a dropdown menu with options to remove or rename the layer (not the actual map), change its display properties (d.rast and d.vect options such as color, symbol, etc.), show its metadata (r.info, v.info) or attributes, if applicable. A left mouse double click on a layer opens GUI for its display options These options are those for the d.* command for each layer type (d.rast, d.vect, or d.grid, for example). Each Map Display Window has a unique layer tree (in the layer manager) and geographic region setting. At the top of the window is a toolbar with buttons to manage the map in the display (render, erase, zoom and pan), for query and and analysis (distance measurement, profile, and histogram creation), to overlay map elements onto the display (scale, north arrow, legend, and custom text), and to export or print the display. In the statusbar, the user can choose to display the geographic coordinates under the cursor, current geographical region extent, computational region (including graphical visualization in map display), map display geometry (number of rows, columns, resolution) and map scale. Checking the render button in the statusbar will cause the map display to update automatically any time a map is added to, removed from, or changed in its layer tree. It is important to note that zooming in any display will have no effect on the ‘computational region’ setting (set with g.region). Only by selecting the ‘Set current region to match display’ item in the zoom menu (in the map display toolbar) will the current display extents be copied to the computational region extents. The GUI can be quit by selecting the ‘File ->, Exit GUI’ menu item. On MS Windows when GRASS is launched without an interactive command line this will end the entire GRASS session. In other cases the terminal window will remain running, type exit at the command prompt to end the GRASS session. The user can also start GRASS from the shell command line with the wxGUI specifying the -gui (or -wxpython) switch: Source.