(1) A hardware interface that transfers one or more bytes simultaneously. See parallel interface.

(2) A socket on a computer used to connect a printer or other device via a parallel interface (eight data bits transferring simultaneously). In the past, the parallel port was widely used for printers and occasionally for connecting other devices externally, but was superseded by USB.

Although some business printers may still offer parallel ports, consumer-based printers and new computers have only USB. However, parallel port devices can be hooked up to new computers with a USB-to-parallel adapter cable.

It Goes Back to the 1970s
The Centronics Data Computer Corporation, a subsidiary of Wang Laboratories in the 1970s, introduced a parallel port for printers. It was adapted for the IBM PC in 1981 and enhanced and standardized by the IEEE in 1994 (see IEEE 1284). The port first appeared on plug-in cards, but was later built into the motherboard. See Centronics interface.