A vehicle control system having program generator and convertor. The system includes a simulation device for simulating actual states such as the actual operating states of an automobile based on various input conditions, a program generation device for generating a control program for an automobile transmission or the like on the basis of the simulated states, a detection device for detecting expressions requiring quantization data included in the control program, a conversion device for converting the detected expressions using a method of notation such as reverse Polish notation, an arithmetic device for multiplying the converted variables by prescribed scaling factors obtained from the quantization factor, and for compressing the expressions multiplied by the arithmetic device. A program generated on a mainframe computer using floating point arithmetic can be translated entirely by machine into a program that can be executed by a microcomputer without using floating point arithmetic.