A screen form is a visual display that can support input or output tasks in an INFORMIX-4GL application. Before your 4GL program can use a screen form, you must first create and compile a form specification file. This is an ASCII source file that describes the logical format of the screen form, and provides instructions to 4GL about how to display data values in the form at runtime. You describe a screen form in its own source file and compile it separately from program code. A compiled form can be used by many programs.

Form Drivers

To work with a compiled screen form, the application requires a form driver, a logical set of 4GL statements that control the display of the form, that binds its fields to 4GL variables, and responds to actions by the user in fields. The form driver can include 4GL screen interaction and data manipulation statements to enter, retrieve, modify, or delete data in the database.

Graphical Windows

Character terminals support only a single graphical window, namely the screen itself. GUI environments allow for multiple graphical windows of many types. The GUI user who runs 4GL applications in a terminal emulator window also works with a single graphical window, the emulator window that displays the character interface of 4GL. By contrast, 4GL for Windows automatically provides several graphical windows for a single 4GL application, usually allowing the user simultaneous access to all of them. This capability to freely address several screens at once is one of the key benefits of GUI platforms and INFORMIX-4GL.

4GL Application Window

Except for Help messages, Line-mode displays, and 4GL report output that is sent to the screen, all 4GL interactive statements appear in the 4GL Application window. The 4GL Application window provides a user interface based on the native GUI format, rather the character format that a terminal emulator uses. The window manager provides the 4GL Application window with a frame containing GUI-standard window controls. The 4GL Application window also typically contains a mouse bar with convenience buttons outside the display area .