ShowDialog XCMD Type 4 displays an "ask" or "answer" dialog that contains a popup menu.
The items in the popup menu are constructed on the fly by passing to ShowDialog a variable containing the items that you would like to appear in the menu, separated by commas. You can modify the style attributes of the individual menu items, enable and disable them, and even attach icons to them, all on the fly.
You also tell ShowDialog which one of the menu items is to be checked when the dialog is initially displayed. When the OK button is clicked, "the result" will contain the item number from the menu that was currently selected.
HyperCard runs on System 3.2 and above, but popup menus were not implemented in the Toolbox until System 4.0. ShowDialog first checks your system configuration and then exits gracefully
(with a beep) if you are running an early system, thus saving you from a fiery crash.