PURPOSE: To raise the mounting efficiency, and to reduce the cost by constituting an input/output processor with an input/output request mechanism, an input/ output control mechanism and a connection processing mechanism.

CONSTITUTION: An input/output processor 10 is constituted of an input/output request mechanism 11 for requesting the input and output of a data to the processor 10, an input/output control mechanism 12 for executing a control to the input and output of a data of the processor 10, and a connection processing mechanism 13 which is connected to the mechanism 11 and the mechanism 12, receives a request from these mechanisms, and responds to their request. According to this constitution, each mechanism is mounted in one enclosure, therefore the mounting efficiency is raised, and also, a signal is sent and received directly between respective mechanisms, therefore, the cost is reduced.