IO is Input (reading data) or Output (writing data).
IO always between Disk and Disk controller. But not memory and Disk.
CPU is processing process p1, in process p1 there is an instruction 'read opd.txt file'. then CPU gives this request to Device controller (disk controller) then disk controller is reading the data from disk and read data should placed in local 'Buffer' of the disk controller.
If some thing need to write then Data should be available in 'buffer' of the disk controller from that disk is reading. because CPU writes the data in massive rate but disk is very slow , so it is not possible to write the data in to disk due the speed. So CPU place the data into disk local buffers from that disk is reading.
IO always between Disk and Disk controller. But not memory and Disk.
CPU is processing process p1, in process p1 there is an instruction 'read opd.txt file'. then CPU gives this request to Device controller (disk controller) then disk controller is reading the data from disk and read data should placed in local 'Buffer' of the disk controller.
If some thing need to write then Data should be available in 'buffer' of the disk controller from that disk is reading. because CPU writes the data in massive rate but disk is very slow , so it is not possible to write the data in to disk due the speed. So CPU place the data into disk local buffers from that disk is reading.
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