To understand how to work with the files opened in the windows, we have to explain first how the program manages them.
After opening an arbitrary data file, the data necessary for work with it (e.g. index file fro the coordinate list, etc.) is loaded into the computer memory and the pertinent file representation is displayed in a window (coordinate lists, drawing, etc.). If the same file is open again, a new window is displayed, but in the computer memory the file is physically opened only once. Therefore, the newly open window is, in fact, really a second "window", through which you look at the same file. There-fore working with graphic plans you can view two different sections of a plan at once.
All that implies is that any change performed to the file in any opened window is physically per-formed on one file. The program indicates this by a consequent numbering of the windows showing one program. If the same part of the file is displayed in more windows, the performed changes are automatically displayed in all the windows.