The traditional parallel port is a 25 "d-sub" connector. Serial ports come in two flavors, either 25 pin "d-sub" or 9 pin. USB (another serial communication standard) is a different animal.PS/2 is...
A common serial port has either nine pins (by far the most common) or sometimes on very old equipment 25 pins. It turns out that they are completely compatible with a very simple adapter... the older...
some have none, especially newer smaller laptops that only have a few usb ports. althought a serial cable to usb connector usually works, the connection is laggier. most computers have one, maybe...