When the PC was first designed, external objects were attached to the console using old ports—specific and appropriately named ports. If you want to attach a keyboard, mouse, or printer, for example, you can use a specific keyboard, mouse, or printer port. Since that time, those old ports on computers have been phased out and replaced with a USB port.
Some common legacy ports are defined as follows:
Mouse and keyboard: The mouse and keyboard ports are designed specifically for what they do: the mouse plugs into the mouse and keyboard port into the keyboard port. And despite the fact that both ports are similar, they are unique, and strange things happen when you connect things incorrectly.
Printer: It should come as no surprise that a computer printer can be plugged into a printer port. But you may not have known that the port was originally called an LPT port. LPT was IBM’s acronym for Line Printer. It may also be called a PRN port.
Serial: The original PC serial port was at one point the most versatile port. Unlike other old ports, you can connect a variety of devices to the serial port: a printer, mouse, modem, and scanner, for example. Unfortunately, the serial devices still required additional setup, and the connection was slow. Therefore, despite its versatility, the functionality of the PC serial port has been taken over by the super USB port.