When a computer receives data from an input device (such as a keyboard, mouse, microphone, etc.), the data must go through an intermediate stage before it can be sent to an output device (like a monitor, printer, speakers, etc). A processing device is any device in a computer that handles this intermediate stage. For example, in the diagram below, the CPU is the processing device.
Processing device examples
Some of the most common processing devices in a computer include the following: