In general, a port is an interface on a computer through which the computer, or more precisely the computer's central processing unit, may be connected to a device. One type of port is termed an I/O port. I/O refers to Input/Output, the communications channel between the computer and the world. It is via the I/O port that peripherals such as printers, external floppy disk drives and monitors can be attached to the computer's processor.

The I/O port is a so-called parallel port. A parallel port is a port through which more than one bit of information can be transferred at a time. On personal computers, the I/O port is a Centronics interface that utilizes a 25-pin connector. Some I/O connections enable up to seven devices to be connected to a computer through the same port.