As we know the drawing compare function in GstarCAD can be used to compare similar drawings containing nearly number of drawn objects to each other, especially to compare different versions of revision drawings.
Menu: Express tools>Drawing Tools>Graphic Compare Command Entry: OCMP
Drawing compare can make comparisons between two similar drawings (old DWG and New DWG) and generate them as separate files. After pressing COMPARE button within CompareDwg dialog box, the program will generate and open _old and _new.dwg files, where you can see the differences between drawings.
Drawing Compare can find out differences (drawn objects) and show the result with different colors, e.g. if a line is modified, removed or newly drawn, it will be displayed in different colors.