Abstract: We propose a method of automatic generation of application specific operating systems (OS's) and automatic targeting of application software. OS generation starts from a very small but yet flexible OS kernel. OS services, which are specific to the application and deduced from dependencies between services, are added to the kernel to construct the whole OS. Communication and synchronization functions in the application code are adapted to the generated OS. As a preliminary experiment, we applied the proposed method to a system example called token ring system.