A printer port, also known as a parallel port, is a hardware interface that hooks up peripheral devices, such as printers, to a central computer system. These ports were originally used to attach many different types of external devices to a computer, although the technology has largely been replaced by the universal serial bus or USB. Before the invention of USB devices, this port was the main form of parallel data transmission to peripheral components.
The development of parallel transmission was a major step forward in the early days of the computer industry. Before devices like printer ports were common, many external devices operated through serial links, which could only transmit one bit of data at a time. Serial technology also sometimes required an additional adapter to connect a computer to a printer or other external device. A printer port using parallel transmission works faster by passing multiple pieces of information between devices using parallel channels. Additionally, the need for an adapter was removed once this type of hardware was mastered.
Most of these ports come in a standard size to make implementation as simple possible. This means that models from different companies will still work when attached, as the port and connecting cable is the same regardless of the manufacturer. The port was originally developed by IBM® as a means of connecting to the early Centronics® printers. The cord used to connect the computer to the printer is very specific, with one 25 prong side to plug into the computer, and one 36 prong side to plug into the printer. When trying to identify if a computer has a parallel printer port, users look for a female port that is long and skinny with two rows of holes.
Originally, parallel ports could only transmit information in one direction, from the computer to the printer. In 1987, however, a bi-directional version was introduced. Today, not only are most of these ports bi-directional, they have also been significantly upgraded to allow information to transmit much faster than original versions.
A printer port will primarily be used to hook up a printer to a central computer, but some other devices may work with this type of port as well. Modems, scanners, fax machines, external drives, and removable zip drives can feature this type of hookup. Since the creation of USB, however, more and more peripheral devices have switched into the new format. Nevertheless, many standard printers still feature this port.