The DM41 is a clone of the HP-41CX including a real-time clock but in the housing of the Voyager series. The alphanumeric LCD screen of the HP-41C revolutionized the way a calculator could be used, providing user friendliness (for its time) and expandability (keyboard-unassigned functions could be spelled out alphabetically). By using an alphanumeric display, the calculator could tell the user what was going on, displaying meaningful error messages ('ZERO DIVIDE') instead of simply a blinking zero. It could also prompt the user for explicit arguments ('ENTER RADIUS') instead of just displaying a question mark.