An observation with Subaru Telescope is designed to be executed by the central scheduler process. Control commands are abstracted common to all observation instruments so that the observers are free from the consciousness of the difference between many instruments as much as possible. An abstraction command which is described in an observation procedure is expanded to a device dependent command script, and the script is dispatched to the telescope and instruments by referring to the instrument table. Device dependent commands are processed synchronously or asynchronously by checking the status against interlocks. The structure of the scheduler and the instrument table, the flow of commands such as an abstraction command, a device dependent command script, and a device dependent command, their examples and syntax are described.