PURPOSE: To input/output (I/O) of data by preparing control information of plural I/O areas in plural controlling tables an I/O controlling means on the basis of plural block I/P information and executing the prepared control information as a channel program.

CONSTITUTION: An application program 12 on a memory 11 sets up parameters, (an address 21 in an I/O data area A on a control table 14, an address 22 in said area B, the length of an address 23 in said area C and said output data, and said areas A15, B16, C17) to process plural blocks and transfers said parameters to an I/O control task 13. The I/O control task 13 decodes the parameters and prepares a control table and a buffer. A channel program is prepared by using the information in the control table and executed in the unit of plural blocks. Consequently the effieiency of the I/O system is improved.