You might have noticed a variety of ports on the back of your CPU casing. There might even be some on the front, on the sides, or the top. Many people are familiar with USB and audio ports. But what are all the other ports, and why do we need them?

If you’ve been wondering this question, then we have this article that is tailored for you. Please read, and enjoy!

A computer port is a junction or a connecting point between a peripheral device and your computer. Peripherals such as keyboards, mice, monitors, speakers, external storage device, etc all need a method to communicate with your computer. 

This is where ports come in. By providing a junction point where the peripherals can attach, they enable the peripherals to communicate with the CPU and carry out their normal functionalities.

As to why there are so many different ports of varying shapes and sizes, the simple answer lies in the fact that various peripherals have varying compatibility, bandwidth, optimization, and shape requirements. There has been some initiative to unify all various port types in the form of USB-C in recent times, however, that does not change the fact that there is still legacy hardware that uses various different types of ports.

Now let’s take a look at the most common computer ports and their functions one by one.

PS/2 ports are 6-pin connectors that were used to connect legacy keyboards and mice. This port was invented by IBM. You usually see two of these ports in older computers, one for a keyboard and mouse each.  

The two PS/2 ports were color-coded and labeled for insertion of keyboard and mouse connectors separately. These two devices use different sets of commands which means the ports were not interchangeable for them even though the ports were physically identical and employed the same communication protocol.

Most modern computers have done away with these ports in favor of USB. Some may provide a single PS/2 port for legacy support, onto which you can insert either a keyboard or a mouse receptacle. 

This is because PS/2 devices do not require drivers, thus they can operate in BIOS. Some USB devices may not operate in BIOS.

The port also inherently supports N-key rollover, which makes them attractive to gamers.

Some corporations might choose PS/2 over USB ports for security reasons.

Also known as COM port, these are communication ports that are used to connect devices such as mice, keyboards, and modems. These ports had either a 9-pin or a 25-pin configuration. These ports support hardware compliant with the RS-232 standard. 

The port was designed for a serial communication interface. Information transfer occurred serially 1-bit at a time and the interface had a bandwidth capacity of 115 KB/s.

These devices have been mostly superseded by USB as well, however, they still find some use in modern hardware where peripherals do not demand much bandwidth capacity, such as Point-of-Sale terminals, industrial automation, some data acquisition systems, etc. 

Also known as LPT port, these ports were designed for the parallel communication interface. These ports had a 25-pin configuration.

In contrast to serial communication, parallel ports allow the transmission of multiple bits of data simultaneously.  These are also commonly identified as printer ports. These ports support the IEEE 1284 standard protocol of communication.

Once ubiquitous, these ports have also been largely replaced by USB ports. Some legacy printers and scanners might still use parallel ports.

FireWire Port was developed by Apple along with Sony and Panasonic, and other companies. It uses IEEE 1394 standard interface. It is also known as i.LINK (Sony) and Lynx (TI).

FireWire ports come in 4-pin, 6-pin, and 8-pin configurations. They are capable of 40 – 500 MB/s data transfer rate. 

FireWire ports are used for transferring audio/video data from digital camcorders. They can also be used for storage media, and to set up improvised ad-hoc networks, which can be set up without the need for a router.

The game port, as the name suggests, was developed as a connector for joystick input for IBM-compatible PCs in the 1980s and 1990s. Like many other legacy ports, these have now been largely deprecated by the use of USB ports.

Game port uses a D-sub connector, also used by the VGA port, that was compatible with four analog channels and four buttons. At the time when they were widely used, they supported two joysticks with two buttons or a single gamepad with an analog stick and four buttons.

The small Computer System Interface (SCSI) interface is used for connecting disk drives and has been around since 1982. SCSI enabled daisy chaining of multiple devices using a single cable. Thus, as opposed to the competing IDE technology of the era, SCSI is capable of connecting up to 7/15 devices at a time. 

Even though the SCSI saw the most widespread adoption for storage devices, it is also able to interface with optical drives and scanners.

Video Graphics Array (VGA) is an analog video interface that uses a D-sub connector with 15 pins. It was first introduced in 1987 with IBM PS/2 computers. 

It is used to send video signals between the computer and a monitor or external display.

Although modern VGA adapters can support up to 2048×1536 resolution, they have largely been displaced by digital interfaces such as HDMI and DisplayPort in recent times.

An audio jack or a headphone jack is used with audio-in and audio-out ports for the transmission of analog audio signals. A standard audio jack is 6.35 mm in diameter. However, for use in personal computers, a miniature size (3.5 mm) is used.

Audio ports can be audio-in, which carries analog audio signals to the computer, for e.g., from a microphone, and audio-out, which carries signals from the computer to an external speaker or headphones.

Some computers have an integrated audio port that can transmit both audio-in and audio-out signals with a single jack.

You can also commonly see these ports in other devices such as your cell phone and speakers. 

The ethernet port or RJ45 is a type of 8 positions 8 contacts (8P8C) connector. They have 8 pins which are the terminal points of 4 sets of twisted pair cables in a cat5/5e/6/6e cable.

Ethernet ports are used for connecting to a network. The Internet Protocol is also carried over ethernet, so they are a key cornerstone in modern internet architecture.

They are capable of data transmission upto 5000 Mbit/s. However, they are commonly used for data transmission upto 1000 Mbit/s.

Digital Video Interface is a video transmission interface developed by the Digital Display Working Group (DDWG) in 1999. The interface can transfer analog (DVI-A), digital (DVI-D), and both digital and analog (DVI-I) signals. The analog mode DVI-A is even compatible with the VGA standard.

The DVI Port has a matrix of square pins that consists of three rows on its left. There can be up to 24 such pins depending upon the mode of DVI interface that is being employed. In the center of the right side is a flat blade, and there can be up to four square pins around the flat pin on either side on the top and bottom. Thus, a DVI port has upto 29 connector pins in it.

DVI connectors come in either a single-link or dual-link variety. Single link DVI has support for resolutions up to 1920×1200 at 60 Hz and dual-link DVI has support for resolutions up to 2560×1600 at 60 Hz. There is even a DMS-59 variant of the DVI port, which can provide two DVI outputs in a single connector.

DVI ports are mostly used for computer video output to a monitor or external display. DVI interface supports High-bandwidth Digital Content Protection (HDCP) protocol, and hence it also sees widespread use in DVD players, HDTV sets, and projectors for transmitting copyright-protected, encrypted video signals.

HDMI Ports are connectors for High-Definition Multimedia Port (HDMI) interface that implements EIA/CEA-861 standards. Its development was started in 2002 by the HDMI founders, which consists of Hitachi, Panasonic, Philips, Sony, Toshiba, Silicon Image, and Thomson. 

There are various types of HDMI connectors available, but the one that is most used is type-A. The standard (type A) connector is 13.9mm x 4.45 mm with 19 pins. The latest version of HDMI (ver 2.1 as of 2022), has a theoretical maximum bandwidth of 48 Gbit/s and can support up to 10K 120 Hz displays. 

The signals carried by HDMI are compatible with DVI, and thus you can use a DVI-HDMI adapter without loss of video quality. Like DVI, HDMI also supports HDPC protocol.

HDMI is used to connect to external displays on PCs, Blu-ray and DVD players, digital cameras and camcorders, consoles, etc. Some cell phone devices also have HDMI video output in the form of a micro-HDMI port. 

HDMI interface is proprietary, hence manufacturers need to pay licensing fee per port for the implementation of HDMI in their devices.

DisplayPort is another video transmission interface based upon outlines standardized by VESA and developed by a consortium of PC and chip manufacturers. Designed in 2006 and starting production in 2008, DisplayPort is one of the latest graphics interfaces in widespread use today. 

There are two types of DisplayPort connectors. The standard connector is a 20-pin, and has dimensions 16.1 mm x 4.76 mm x 8.88 mm. It also has an option for a mechanical latch. The mini-DisplayPort connector also has 20 pins with dimensions 7.5 mm x 4.6 mm x 4.9 mm. It lacks the option for a mechanical latch.

The latest version, DisplayPort 2.0, was announced in 2019 and can support up to 16k @ 60 Hz resolutions on a single screen. It is compatible with HDMI and DVI standards with simple passive adapters. 

It has support for Multi-Stream Transport (MST), which means multiple independent displays can be connected to a single DisplayPort port. Other features include DisplayPort Content Protection (DPCP), support for HDCP,  and implementation of High Dynamic Range (HDR) standards.

The Universal Serial Bus is a standard of data transfer, communication, and power supply that was first introduced in 1997. There exists a wide variety of USB ports (14 in total till date), of which type-A and type-C are the most prevalent.

The USB standard has undergone numerous revisions. The various version of USB so far are:

The type-A plug has an elongated rectangular shape and has 4 pins in total. Two of them are for data transfer and two for power transfer. The pins for data transfer are slightly recessed compared to the power pins.  However, USB 3 and newer standards have 5 additional pins for increased bandwidth and power transfer capabilities, for a total of 9 pins.

The type-C connected is also an elongated rectangular, but with sides that are curved. The connector/plug has 24 pins and is double-sided. This port was designed with future-proofing in mind. 

Today, the USB standard has found its use in the following applications:

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