A digital instrumentation system for automobiles is developed using a single card computer whose CPU is Z-80. Specifically this system consists of 4 subsystems, such as, HEI system, microprocessor based ignition control, hardware for display, software display. Among them, implementation and software development of the hardware for display and the software for display are mainly studied. It is noted that first, the interrupt driven method is employed as an interfacing technique for the communication between microcomputer and the peripherals and sensors developed here. Second, the quantities to be displayed on a digital panel of automobile are trip speed, clock, voltage, coolant temperature, and trip time, and time multiplexing method are also employed as their displaying technique. It is also noted these quantities are only displayed during the time when the microprocessor is not required by the engine ignition timing controller. Many software sheme and the experimental results are also included.