With both programmed I/O and Interrupt driven I/O, the processor is responsible for extracting data from main memory for output operation and storing data in main memory for input operation.
To send data to an output device, the CPU simply moves that data to a special memory location in the I/O address space if I/O mapped input/output is used or to an address in the memory address space if memory mapped I/O is used.

To read data from an input device, the CPU simply moves data from the address (I/O or memory) of that device into the CPU.

Input/Output Operation: The input and output operation looks very similar to a memory read or write operation except it usually takes more time since peripheral devices are slow in speed than main memory modules.

The working principle of the three methodds for input of a Block of Data is shown in the Figure 6.2.