What devices are connected to the COME port on a computer's mainframe?

Nowadays, few devices use this interface. In the past, the mouse is useful for this kind of interface, and now most of the professional equipment is still in use.

Computer COM port is actually called a serial port, just an English one Chinese only, connected to a lot of equipment, for example, as follows:

Hospital medical equipment control, such as hospitals, gastroscopes, CT, chest X-ray machine.

Supermarket charge related equipment, such as supermarkets with small ticket printers, card machines, bar code rob and so on.

Engineering production design control, such as PLC programmer.

Computer expansion peripheral devices, such as printers, serial mouse, serial keyboard.