In addition to an IRQ, computer components
also need to be assigned an I/O port number. An I/O port number is a
memory address where data is temporarily stored as it moves in and out
of the devices. The I/O address is very similar to a post office box.
As mail comes in, it is stored temporarily in a post office box. No
two boxes can have the same number or the mail can end up in the wrong
box. The same is true for I/O ports. No two devices can have the same
I/O address. Table
shows I/O settings for common input and output devices.
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