This paper describes the man-machine interface and control software of a Navigation System for private automobiles. The system shows the accurate position of the vehicle on a CRT map display and can also provide useful information such as the locations of hotels, golf clubs, etc.The man-machine interface of this system consists of a menu display and touch-sensitive switches on the screen. Due to safety considerations, some of the displays and operations are prohibited while the vehicle is in motion.A multi-tasking software system controls these functions. Most of the programs were written in “C”, but assembly language was used for some basic input/output control programs. The total program size is about 384 Kbytes.This navigation system was installed in Mitsubishi's Diamante models in 1990.