| 摘要 |
PURPOSE:To suppress the meaningless activation of I/O devices and to enhance the efficiency of handling actions regarding input and output by providing flags displaying whether the I/O devices are busy or not. CONSTITUTION:The I/O devices 31-3n are provided with the respective one-bit control flags 9. They set the one-bit flag corresponding to the I/O device to 'ON' when a subchannel awaiting an I/O request succeeds in the activation of any of the I/O devices 31-3n, and resets an interruption when the interruption from the I/O device is reported at the end of the I/O actions. If the flag corresponding to the I/O device concerned is turned on (another subchannel is using the device) by referring to the control flags 9, the subchannel is connected to the end of an I/O request queue without trying activation. |
