WINDOW allows you to specify entities using a window.  
The cursor is used to indicate the opposite corners of 
the window with a rubberbox.

Indicate a corner of the window by moving the cursor to 
the desired position on the screen, and pressing the 
cursor button or, by pressing the space bar and entering 
the x and y view coordinates.  When the cursor is moved, 
a rubberbox is connected to this first position.

Indicate the opposite corner of the window by moving the 
cursor to the desired position on the screen, and 
pressing the cursor button or, by pressing the space bar 
and entering the x and y view coordinates.

