WINDOW OUTPUT [#]idExpr
This statement makes an existing window the current output window. The current output window is the destination for any subsequent text and drawing commands, and is the target window for such statements and functions as
EDIT FIELD, etc.
idExpr can be either a positive or negative number;
WINDOW OUTPUT affects the window whose ID number is
ABS(idExpr). If you specify a negative
idExpr, the window becomes invisible. If you specify a positive
idExpr, the window becomes visible.
WINDOW OUTPUT does not activate the specified window (i.e., it does not highlight its contents nor bring it to the front), if there are other visible windows open. Use the
WINDOW statement when you want to explicitly activate a window. (Note: the
WINDOW statement also makes the specified window the current output window.)
WINDOW OUTPUT is useful in cases where you need to update the contents of a window which may be in the background, without bringing the window to the front.