Computer Ports and Their Functions
Computer Ports and Connectors
This article describes the nature of each of the main external computer ports, their connector types, and common modes of use.
A port is a connector at the back or side of a computer where you plug in an external device such as a printer, keyboard, scanner, mouse, or modem. This connection allows instructions and data to flow between the computer and the device. These computer ports are also commonly referred to as the Input/Output ports (I/O ports).
Most Connectors are Polarized
Most connectors are polarized, permitting the cable to be plugged in only in one correct direction. The keyboard and mouse use "PS2" connectors which are color-coded: The purple connector is for the keyboard while the green connector is for the mouse.
Connecting a Keyboard/Mouse to Your Computer
To plug in a keyboard or mouse cable, first match the cable to the connector. Rotate the cable until the connector keys match up with the receptors, then push the cable in. Be sure not to force the connector because you will end up bending the pins.
The parallel port, serial port, and video port all use D type connectors (DB-25M, DB-9M, and DB-15F, respectively). These are called "D connectors" because of their shape, which permits the cables to be plugged in only one way.
The audio jacks are the most confusing connectors on the back panel. Although the jacks are sometimes color-coded, the devices that plug into them rarely are. You can try using the identifying symbols stamped into the metal next to them.
The green jack (audio out) is where you plug in your left speaker. Only one speaker plugs into the computer: The right speaker plugs into a jack on the left speaker.
The red jack is where you plug in your microphone. The center jack (audio in) is where you plug in audio from another device, such a CD player.
A computer cable connector is the part of a cable that plugs into a port or interface to connect a device to the motherboard or another device. Most connectors are either male (containing one or more exposed pins) or female (containing holes in which the male connector can be inserted). A number of different connector types are used to connect various external devices to the computer.
This connector type is most often associated with the serial, parallel, and display monitor ports. DB stands for D bucket connector and the full connector designation (e.g. DB25 male) refers to the number of pins in the connector and whether the connector is a male (plug) or female (socket) type.
Note: If a DB-type port uses a female connector, the cable associated with the port will require a male connector to ‘mate’ correctly and vice versa.
The standard 15-pin VGA connector was derived from an older 9-pin design; consequently, the plugs have 15 pins in a connector shell originally designed for 9. The only way to make more pins fit was to make them thinner, but this also makes them more prone to bending, so always take care when plugging in video leads because bent pins are hard to straighten without breaking them off. The monitor might work with a bent pin, but you will not get the correct colour output.
The DIN Connectors
Another type of connector is the DIN connector. DIN is an abbreviation for Deutsches Institut für Normung, or German Institute for Standardization, which is a German manufacturing industry standards group. DIN connectors are round with pins arranged in a circular pattern. This type of connector was used widely for PC keyboards, MIDI instruments, and other specialized equipment.
We have two types of DIN: Full DIN and Mini DIN.
Full DIN (or five pin DIN):
This connector has five pins that are arranged in a circular pattern. This type of connector was commonly used for older AT-style computer keyboards that are obsolete nowadays.
This connector has six pins as well as a keying block. This interface was first used on the IBM PS/2 personal computer. For this reason, the connector is often called a PS/2 connector. This connector, which had become the industry standard for connecting keyboards and mice, has been superseded by the USB connector.
Most of the audio connectors on a PC are 3.5 mm mono and stereo jack plugs, as used on most portable domestic audio equipment. Using them, you connect computer speakers or headphones to get sound out of your computer.
The USB Port
USB stands for universal serial bus. This is an industry standard computer bus developed in the mid-1990s that replaced some ports we used, for instance, the PS/2 ports for mouse and keyboard.
The USB standard defines the cables, connectors, and communication protocols used in a bus for connecting devices, enabling communications and providing power between the PC and the device. After it was developed, the USB became the standard for connecting most computer peripheral devices such as modems, keyboards, mice, printers, scanners, digital cameras, disk drives, PDAs, smartphones, and a host of other devices.
Features of the USB Port:
- It supports plug-and-play: Once connected, the device is configured automatically without any user input.
- It supports hot swapping: Devices can be plugged and unplugged while the computer is powered on. Note that it is always recommended to eject manually using the "safely remove hardware" instruction before unplugging from the computer.
- It supports 127 peripheral devices (you can make use of a USB hub for more additional ports).
- It provides power to connected devices.
Data Transfer Rates of Typical USB Ports
DATA TRANSFER RATE IN Mbps
1.5 & 12
1.5 & 12
USB 2.0 (high speed)
USB 3.0 (super speed)
Do you know most of the computer ports at the back of your computer?
© 2011 Patrick Kamau