This paper deals with the personal computer based design for the sequential machines. Most part of sequential machine design have been implemented by using general purpose microprocessors in order to obtain the specific unctions required for their system. But, they have some difficulties in design stages. Knowledge of systems design method and high technology are basically applied to all the design stages.. Therefore ready made microcomputer system for personal use, personal computer, can be transformed to sequential machines by using the corresponding softwares and built-in personal computer input/output ports. Following the state transition diagram or table, we can obtain the ROM type of sequential machines directly and need not to design input/output interface except actuators and samplers because of capability of personal computer. Our main purpose of this design method are quick, flexible, reliable, modifiable circuit design of the sequential machines. In this paper, we use APPLE-II plus personal computer as target machine.