An input-output processor (IOP) handles input/output (I/O) tasks by directly accessing and storing data in memory without involving the CPU. It acts as an interface between the computer and I/O devices. When an I/O device needs to access or store data in memory, it requests the DMA controller, which sends a hold request to the CPU. The CPU acknowledges and the DMA controller allows for direct data transfer between the I/O device and memory without CPU involvement. This speeds up I/O tasks and reduces CPU overhead.

1. What is Input output processor ?
An input-output processor (IOP) is a special processor used in DMA
that can directly access and store data into memory. It is similar to a
CPU, except that it only handles the tasks of I/O processing. It acts as
an interface between the computer and the I/O devices.

2. Working of Input-Output Processor
1.When an I/O device has to access or store data to memory, it
requests the DMA controller. The DMA controller then sends a Hold
request (HLD) to the CPU to hold.
2.The CPU, on receiving the Hold request, sends Hold
acknowledgment (HLDA) to the DMA controller.
3.After receiving the HLDA, the DMA controller allows the data transfer
and takes charge of the system bus.
4.On completion of the data transfer, the DMA again issues an
interrupt, letting the CPU know that the data transfer has finished.
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3. Fig: input output processor.

4. Advantages of Input-Output processor
1.Speeds up the read-write operations as it does not involve a
processor.
2.I/O devices can access the main memory directly.
3.Reduces the CPU overhead of waiting for I/O to complete.

5. Disadvantages of Input-Output processor