Understanding Parallel Ports

A parallel port is either an input or output port that supports parallel communication. Parallel communication occurs when data is transmitted and processed one byte at a time. Eight transmission lines carry the signal. Parallel communication is typically faster than serial communication.

parallel communication

The process of transmitting and processing data one byte(8 bits)at a time.

byte

A single binary character, or 8 bits.

Extended Capabilities Port (ECP)

The standard developed for parallel communication by Hewlett-Packard and Microsoft to allow for data-transfer rates of more than 2MBps. In addition to the high data-transfer rates, it allows for bidirectional operation.

Enhanced Parallel Port (EPP)

The standard developed for parallel communication by Intel, Xircom, and Zenith Data Systems to allow for data-transfer rates of more than 2MBps. It supports bidirectional operation of attached devices and an addressing scheme.

Most parallel ports today are based on the Extended Capabilities Port (ECP) or Enhanced Parallel Port (EPP) standards that support data transfer speeds of more than 2MBps.

Parallel communication is often used to connect printers. Although parallel communication is not the fastest communication method, it is a cost-effective solution. Almost all computers today are built with a parallel port.

Besides printers, parallel ports can also support external storage devices (discussed in Chapter 2, 'Storing Your Files: Data Storage'). External devices that communicate using the parallel port connect via a 25-pin female connector.

Note 

The original parallel port was designed to send information in one direction to a printer. Standards were later developed to improve the capabilities of the parallel port by allowing communication to occur in both directions and supporting multiple devices on the same port.

USB hub

A connectivity device that provides multiple USB connections so that several USB devices can communicate with the computer.

megabits per second (Mbps)

A measurement of the amount of data, in the millions of bits per second, being transferred.

bandwidth

The capacity of a network line to carry information. Bandwidth is best thought of as a highway; four lanes support more traffic than two and have fewer slowdowns. One of the few basic rules of modern networking is that more bandwidth is always better.