PURPOSE: To avoid a setting mistake and to improve the application performance of a titled system, by transferring the constitution controlling information which is held at a main storage device by an operating system to the storage area within a channel device by an instruction given from a central processor.

CONSTITUTION: A CPU20 gives three instructions, i.e., a test IOCW, a read IOCW and a write IOCW to a channel device CH10 by an input/output instruction code signal 28. An instruction IOCW means a constitution controlling information word, and plural numbers of this information word are held at a storage area 14. Then the instruction IOCW that receives access is known by an address signal 29. The code signal 28 is decoded 23, and decoded signals 31W33 are fed to a CH main control part 22. The signals 31W33 correspond to above-mentioned three instructions, and the part 22 works in response to these three instructions. The execution result of instructions is informed to the CPU20 with a state code 30. Thus an operating system itself offers the constitution controlling information to the CH. This system prevents completely a manual setting mistake.