A program generation program used in a personal computer processes information on relationship between an action and a pair of a state of a system and an event to create a program for incorporating a new state in a state transition table. The computer reads the state transition table in a storage medium and selects the state specified in the state transition table. The computer generates a program that determines whether the selected state is an exceptional state or a normal state on the basis of state information in the state transition table. Based on the result of the determination, the program performs an action including a state transition or a process allocated to the exceptional state specified in the state transition table when the state is the exceptional.