Futurebasic/Language/Reference/window close

Syntax
WINDOW CLOSE [#]windowID

Description
This statement closes the window whose ID number is, removing it from the screen. It also closes all edit fields, picture fields, buttons and other controls that were in the window. If you re-use the same  value in a subsequent   statement, a new window is created.

If you're closing the active window, and your program has other visible windows open, one of the other windows becomes the active window, and becomes the current output window. If you're closing the current output window (but it's not the active window), you should explicitly designate a new destination for output (using the  statement or the   statement) before executing any subsequent text or drawing commands.