The input/output (I/O) ports
Computer I /O (input/output) ports allow the CPU to control devices in the outside world. Signals may be output to control lights, motors and heaters for example. Conversely, signals from the outside world, provided by sensors such as simple switches, thermistors, opto diodes (light sensors) and pressure sensitive devices, may be input to the CPU. These signals can be analysed and processed, with the CPU outputting new signals in consequence. So, like sea ports along the coast which allow goods to be brought into and out of a country, I /O ports allow signals to pass into and out of a computer.