How to define MCU port with C language?

The interface of single chip microcomputer refers to all external channels connected to the single chip microcomputer system, such as RS232 interface, etc;


The port refers to the direct output and input ports of these microcontrollers.


Therefore, the definition of port is to define each pin directly. Take 51 as an example:


51 port classification method of single chip microcomputer: P0, P1, P2, p3


This represents a group of pins, each group has 8 pins; If P0 is composed of p0.0, P0.1, P0.2 P0.7 consists of 8 pins in total.