Serial Port and Parallel port

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Every computer is built with tons of different ports that perform various functions. Two of the most important types for data trans are serial ports and parallel ports.

This article will explain to you the differences and similarities between the two types of port.

Serial Ports

Serial ports are generally built into the mother board, which is why the connectors behind the casing that are connected to the mother board by a wire cable can be used to connect an exterior element. Serial connectors generally have 9 or 25 pins and resemble the following (DB9 and DB25 connectors respectively):

DB9 connector

DB25 connector

A personal computer generally has between one and four serial ports.

Parallel Ports

Parallel data transmission involves sending data simultaneously on several channels (wires). The parallel ports on personal computers can be used to send 8 bits (one octet) simultaneously via 8 wires:

transmission on a parallel port

The first two-way parallel ports allowed for speeds of 2.4Mb/s. Enhanced parallel ports have been developed however to achieve higher speeds — the EPP (Enhanced Parallel Port) achieves speeds of 8 to 16 Mbps, and the ECP (Enhanced Capabilities Port), developed by Hewlett Packard and Microsoft has the same characteristics as the EPP, with a Plug and Play feature, allowing the computer to recognise the connected peripherals.

Parallel ports, like serial ports, are built into the mother board. DB25 connectors allow for connection to an exterior element (e.g. a printer):

DB25 connector

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Jean-François Pillou

Jean-François Pillou - Founder of CCM
Better known as Jeff, Jean-François Pillou is the founder of He is also CEO of CCM Benchmark and digital director at the Figaro Group.

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