PURPOSE: To shorten a processing time by a simple constitution by transmitting a logical input/output number to an input/output control device so that it is unnecessary that a CPU executes a surplus table search at the time of the end interruption, when executing the input/output start.

CONSTITUTION: In case when an input/output request is executed from a program, a logical input/output number is converted to a physical input/output address by a table 4 in the same way as a conventional system. By this physical input/output address, its input/output number is transmitted as an additional information to an input/output control device 3, and it is stored in a logical number storage register 5. When this input/output operation is ended, an input/ output interruption is transmitted to a CPU 2, and the CPU 2 executes recognition of an interruption addrdess. In this case, in addition to the physical input/ output address, the logical input/output number stored in the register 5 of the device 3 is transmitted together.