The third and fourth of the five elements are an input and an output.
I/O is a function for exchanging data and signals between external devices and a microcontroller.
Peripheral circuits dedicated to external devices are prepared, and they perform input, output, and communication of data.
Basic operation includes "read" and "write" by the CPU.
I/O is called "Port", and its address is called "Port address."
There are "Input port" and "Output port" depending on the exchange of the data and signals with external devices.