### Actions and Buttons in “Window” mode

The “Main panel window” is created when command GUIGO is typed. Four buttons are defined by default in this window:

- the OK button,
  which sets all variables defined in the main and sub-panel windows. This button also executes the command passed as argument to the GUIGO command (if specified).
- the UPDATE button,
  which sets all variables defined in the main and sub-panel windows, without executing the (optional) command passed as argument to the GUIGO command.
- the ABORT button.
  Variables are not modified, and an error is sent to the main program.
- the HELP button.
  This button displays the help file specified in the GUIPANEL command.

Additional buttons can also be added to the “main panel window” using the GUIBUTTON command. Two types of buttons exist

- Buttons with no associated parameters. These buttons appear just after the 3 main buttons.
- Buttons with optional parameters. These buttons appear sequentially with the variables, and have an associated parameter or “optional” window. When such a button is defined, all subsequent LET commands create a widget in a “sub-panel” window. This window is by default hidden, but can be unveiled by the user.

The “sub-panel” windows provide a way to hide some non-essential parameters, and/or to create a “main window” with a control panel defining many actions, each action having its own input window and separate help.