The .4gl File - Opening Windows and Forms

A program creates a window with the OPEN WINDOW instruction, and destroys a window with the CLOSE WINDOW instruction.

The OPEN WINDOW ... WITH FORM instruction can be used to automatically open a window containing a specified form:
OPEN WINDOW custwin WITH FORM "custform"

When you are using a graphical front end, windows are created as independent resizable windows. By default windows are displayed as normal application windows, but you can specify a Presentation Style. The standard window styles are defined in the default Presentation Style file (FGLDIR/lib/default.4st):

If the WITH FORM option is used in opening a window, the CLOSE WINDOW statement closes both the window and the form.
When the runtime system starts a program, it creates a default window named SCREEN. This default window can be used as another window, but it can be closed if not needed.
Note: The appropriate Genero Front-end Client must be running for the program to display the window and form.