Legacy Ports on a PC
When the PC was first designed, external thingamajigs were attached to the console by using legacy ports — specific and aptly named ports. If you wanted to attach a keyboard, mouse, or printer, for example, you would use a specific keyboard, mouse, or printer port. Since that time, those older legacy ports have been phased out on PCs and replaced by the 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 port, and the keyboard into the keyboard port. And, despite the fact that both ports look alike, they’re unique, and strange things happen when you connect things improperly.
Printer: It should be no surprise that the computer’s printer can plug into the printer port. But you probably didn’t know that the port was originally called the LPT port. LPT was an IBM acronym for Line Printer. It may also be called a PRN port.
Serial: The original PC’s serial port was at one time the versatile port. Unlike with the other legacy ports, you could plug in a variety of devices to the serial port: printer, mouse, modem, and scanner, for example. Sadly, serial devices still required extra setup, and communication was slow. Therefore, although versatile, the function of the PC’s serial port has been taken over by the superior USB port.