Computer Ports: What are They?

A port is a physical docking point for an external device to be connected to the computer. It can also be a programmatic docking point through which information flows from a program to the computer or over the Internet.

Characteristics of Ports

A port has the following characteristics:

  • External devices are connected to a computer using cables and ports.

  • Ports are slots on the motherboard into which an external device cable is plugged.

  • Examples of external devices attached via ports are the mouse, keyboard, monitor, microphone, speakers, etc.

Optical Audio “Toslink”:  Toslink, also known as optical audio, is a type of digital audio cable that uses fiber optic technology to transmit audio signals between devices The name “Toslink” is derived from the original name “Toshiba Link”.  Toslink cables use light pulses to transmit digital audio signals, which makes them distinct from other types of audio cables that use electrical signals. They are commonly used to connect audio equipment such as soundbars, home theater systems, and gaming consoles to TVs.

USB A (1.0, 1.1, 2.0):  USB-A is a type of USB connector that has been used in various versions of the USB standard. USB 1.0, 1.1, and 2.0 are different versions of the USB standard that use USB-A connectors.  USB 1.0 was the first version of the USB standard and was released in 1996. It had a maximum data transfer rate of 12 Mbps. USB 1.1 was released in 1998 and had a maximum data transfer rate of 12 Mbps as well. USB 2.0 was released in 2000 and had a maximum data transfer rate of 480 Mbps.

Firewire 400 1394a:  FireWire 400 is a type of IEEE 1394a interface that is used for high-speed data transfer between devices. It is also known as i.LINK and has a maximum data transfer rate of 400 Mbps.

Firewire 800/3200/1394 b/c: FireWire 400 is a type of IEEE 1394a interface that is used for high-speed data transfer between devices. It is also known as i.LINK and has a maximum data transfer rate of 400 Mbps.

Ethernet 8P8C (Common RJ-45):  Ethernet 8P8C is a type of connector that is used for Ethernet networking. It is also known as RJ45 connector. The name “8P8C” stands for “eight positions, eight contacts”.  The Ethernet 8P8C connector has 8 pins and is used to connect Ethernet cables to devices such as computers, routers, and switches. It is the most common type of connector used in Ethernet networking.

Modem RJ-11:  RJ-11 is a type of connector that is used for telephone and modem connections in the US. It has 4 or 6 pins and is commonly known as a modem port, phone connector, phone jack or phone line.

Apple Desktop Bus -ADB:  Apple Desktop Bus (ADB) is a proprietary bit-serial peripheral bus that was used to connect low-speed devices like keyboards and mice to Apple computers. It was introduced in 1986 on the Apple II GS and was later used on all Macintosh models until it was replaced by USB in 1999. The ADB connector is a Mini-DIN-4 connector that has 4 pins.

Mac Serial:  A serial port is a connector on a computer to which a serial line can be attached to communicate with peripherals that communicate through a serial (bit-stream) protocol. On Mac, serial ports are usually identified as /dev/tty.* or /dev/cu.*.

PS/2: A PS/2 port is a 6-pin mini-DIN connector used for connecting keyboards and mice to a PC-compatible computer system. The name comes from the IBM Personal System/2 series of personal computers, with which it was introduced in 1987. The PS/2 mouse connector generally replaced the older DE-9 RS-232 “serial mouse” connector, while the PS/2 keyboard connector replaced the larger 5-pin/180° DIN connector used in the IBM PC/AT design.

USB A 3.0: USB-A 3.0 is a specific type of USB connector that supports SuperSpeed data transfer rates of up to 5 Gbit/s 1. The USB-A 3.0 connector has 9 pins and is backward compatible with USB 2.0 ports, which have 4 pins 2.

DE-9F:  A DE-9F port is a type of D-subminiature connector with an E shell that is used for RS-232 serial communication. It is often confused with the DB-9 connector, which is also a D-sub connector but has a smaller shell size. The DE-9F port is also known as a COM port and allows full duplex serial communication between the computer and its peripherals.

DB-25 Serial/Com Port: A DB-25 connector is a type of electrical connector that is commonly used for serial communication. It is also known as a D-subminiature or D-sub connector, named after its characteristic D-shaped metal shield. The DB-25 connector has 25 pins and is primarily used for serial connections, allowing asynchronous transmission of data provided by standard RS-232 (RS-232C).

DE-9 Serial RS232:  DE-9 is a 9-pin connector that was commonly used for serial communication between devices. It is also known as RS-232 or DB-9. The DE-9 connector was the industry standard for serial data transmission and was used to connect modems, keyboards, mice, external storage, and many other peripheral devices to personal computers.

e-Sata:  External Serial Advanced Technology Attachment. It is an extension to the Serial ATA standard that enables SATA drives to connect to your computer externally. It is an industry-standard for controlling the various hardware used to connect external storage devices. It competes with some Firewire and USB standards to provide faster data transfer speeds between hardware devices. Compared to USB and FireWire, eSATA offers faster data transfer speeds. It is also hot-swappable, meaning that drives can be added or removed from a system without shutting down the computer. The port multiplier feature of eSATA allows a single eSATA connector to be used to connect an external eSATA chassis that provides multiple drives in an array.

Centronics Parallel 36 PIN:  Centronics Parallel 36 PIN is a type of connector that was commonly used for parallel communication between computers and other devices such as printers and scanners. The connector has 36 pins arranged in two rows of 18 contacts each and is held in place by bail locks. The Centronics port was later replaced by the DB-25 port with a parallel interface.

Centronics SCSI 50 PIN:  The Centronics SCSI 50 PIN is a type of connector used in SCSI-1 applications such as older scanners, controllers, and external SCSI device cases. It has 50 pins arranged in two rows of 25 pins, one on top of the other. The connector is similar to the 36-pin connector used by Centronics for the parallel interface on their printers, thus the connector became popularly known as “Centronics SCSI” or “CN-50”.

AT Keyboard:  An AT keyboard, also known as the Model F keyboard, is a US standard keyboard introduced in 1986 by IBM. The original version had 84 keys but was then replaced by the 101-key-enhanced keyboard.

50-Pin SCSI 2:  50-Pin SCSI 2 is a type of SCSI connector used to connect computer parts that use a system called SCSI to communicate with each other. The Micro DB50 or MD50 connector is a type of 50-pin SCSI-2 connector that has 50 pins arranged in two rows of 25 pins, one on top of the other. It is typically used in SCSI-2 applications such as scanners, removable storage drives, controllers, and external CDR/CDRW.

Surround Sound:  Surround sound is a technique for enriching sound reproduction by using multiple audio channels from speakers that surround the listener. It can create the sensation of sound coming from any horizontal direction around the listener and enhance the illusion of live hearing. It can also add a whole new dimension to the video enjoyment. To experience surround sound, one needs media with audio mixed for surround sound, a proper AV receiver, and an assortment of speakers properly placed around the sitting area. There are different formats and configurations of surround sound for home theater systems. Some people prefer all-in-one bundles, others prefer multi-speaker packages, and others prefer computer speakers.

Stereo Headphones/Line In/MIC:  A line-in is an audio socket on audio interfaces, computer sound cards, and some mixers. It connects an external audio device such as an instrument, microphone, or CD player. Conversely, a mic-in is designed for microphones – you connect a wired or wireless mic to a mic-in. A stereo headphone is a pair of headphones that reproduces sound in both ears. It is designed to be used with devices that have a 3.5mm headphone jack. The line-in and mic-in are types of audio inputs, but they are indicative of the voltage level of the audio signal. Line-in can handle strong (think loud) currents, whereas a mic-in can handle very low current levels.

Digital Audio RCA Plug Style: The RCA connector is a type of electrical connector commonly used to carry audio and video signals. It was introduced by the Radio Corporation of America in the 1930s. The connector’s male plug and female jack are called RCA plug and RCA jack, respectively. The RCA plug consists of two rows of three-terminal contact pins connected to the cable shields with a central pin. The pins are typically colored red (hot), white (cold), and black (ground) 2. A coaxial digital connection uses a single RCA connector, usually orange or black, to transmit digital signals. Unlike stereo analog audio, which requires two cables for stereo, coaxial only needs one.

AAUI:  The Apple Attachment Unit Interface (AAUI) is a mechanical redesign by Apple of the standard Attachment Unit Interface (AUI) used to connect Ethernet transceivers to computer equipment. The AAUI was introduced in the early 1990s as an attempt to make the connector much smaller and more user-friendly, though the proprietary nature of the interface was also criticized. The AAUI is part of a system of Ethernet peripherals intended to make connecting over Ethernet much easier. At the time of the introduction of AAUI, Ethernet systems usually were 10BASE2, also known as thinnet. Apple’s system is called FriendlyNet. Macintosh Quadra, Centris, PowerBook 500, Duo Dock II (for PowerBook Duo), and early Power Macintoshes have AAUI ports, which require external transceivers. By the time AAUI was nearing the end of its life, an AAUI transceiver could cost even more than an inexpensive Ethernet card on a PC.

Composite Audio/Digital:  Composite audio is a type of analog audio signal that combines multiple audio signals into a single signal. It is usually transmitted using RCA connectors, which are color-coded red and white.  Digital audio is a type of audio signal that is transmitted in a digital format, which means that it is represented by a series of 1s and 0s. The RCA connector is a type of electrical connector commonly used to carry audio and video signals. It was introduced by the Radio Corporation of America in the 1930s. The connector’s male plug and female jack are called RCA plug and RCA jack, respectively. The RCA plug consists of two rows of three-terminal contact pins connected to the cable shields with a central pin. The pins are typically colored red (hot), white (cold), and black (ground). A coaxial digital connection uses a single RCA connector, usually orange or black, to transmit digital signals.

S-Video:  S-Video is an analog video connection standard that transmits electrical signals over wires to represent the original video. It is also known as Super-Video. S-Video technology transmits standard-definition video with 480 pixels or 576 pixels resolution. The S-video cable transmits video through two synchronized signal-and-ground pairs, named Y and C: Y is the luma signal, which carries the luminance or the black-and-white elements of the video. It also includes horizontal and vertical synchronization pulses. C is the chroma signal, which carries the chrominance, the color portion of the picture. This signal includes both the saturation and hue elements of the video. S-video cables have a variety of uses, including connecting computers, TVs, DVD players, video cameras, and VCRs. S-video is an improvement over composite video, which carries all the video data (including brightness and color information) in one signal over one wire. S-video carries brightness and color information as two separate signals over two wires. Because of this separation, video transferred by S-video is of higher quality than composite video. 

Component Video:  Component video is an analog video signal that has been split into two or more component channels. It is a type of component analog video (CAV) information that is transmitted or stored as three separate signals. The three separate signals are usually referred to as Y, Pb, and Pr. Y represents the brightness of the image, while Pb and Pr represent the color information. Component video provides a sharper image than composite video and S-video, which multiplex the signals together. Component video cables and their RCA jack connectors on equipment are normally color-coded red, green, and blue, although the signal is not in RGB. 

F-Connector RF/Coax:  The F connector is a type of coaxial RF connector commonly used for “over the air” terrestrial television, cable television, and universally for satellite television and cable modems, usually with RG-6/U cable or with RG-59/U cable. It is an inexpensive, gendered, threaded, compression connector for radio frequency signals. The F connector has a good 75Ω impedance match for frequencies well over 1 GHz and has usable bandwidth up to several GHz.  The male plug and female jack are called RCA plug and RCA jack, respectively. The F connector was invented by Eric E. Winston in the early 1950s while working for Jerrold Electronics on their development of cable television. 

Parallel Port/SCSI 1/DB-25F:  A parallel port is a type of computer interface commonly used to connect printers to the computer. It is found on the back of IBM-compatible computers and is a 25-pin (type DB-25) connector. Parallel SCSI (formally, SCSI Parallel Interface, or SPI) is the earliest of the interface implementations in the SCSI family. SPI is a parallel bus; there is one set of electrical connections stretching from one end of the SCSI bus to the other. A SCSI device attaches to the bus but does not interrupt it. Both ends of the bus must be terminated. The DB-25 connector is a 25-pin electrical connector for serial and parallel computer ports. It is arranged in rows of two with one 13-pin row above another 12-pin row. The DB-25 connector is used for parallel, small computer system interface (SCSI), or RS-232 serial applications. 

Mac Video/MIDI/Gameport/AUI/DA-15:  MIDI stands for Musical Instrument Digital Interface. It is a technical standard that describes a protocol, digital interface, and connectors and allows a wide variety of electronic musical instruments, computers, and other related devices to connect and communicate with one another.

Mini Display Port:  The Mini DisplayPort is a miniaturized version of the DisplayPort audio-visual digital interface. It was announced by Apple in October 2008 and is used to connect a video source to a display device, such as a computer monitor. The Mini DisplayPort is a 20-pin connector that is smaller than the standard DisplayPort connector. It can support resolutions up to 2560×1600 (WQXGA) in its DisplayPort 1.1a implementation, and 4096×2160 (4K) in its DisplayPort 1.2 implementation. With an adapter, the Mini DisplayPort can drive display devices with VGA, DVI, or HDMI interfaces. 

Mini DVI:  The Mini DVI is a video connector used on certain Apple computers as a digital alternative to the Mini-VGA connector. It is smaller than the full-sized DVI and larger than the tiny Micro-DVI. The Mini DVI plug has 32 pins arranged in two vertically stacked slots, and it is found on the 12-inch PowerBook G4 (except the original 12-inch 867 MHz PowerBook G4, which used Mini-VGA), the Intel-based iMac, the MacBook Intel-based laptop, the Intel-based Xserve, the 2009 Mac mini, and some late model eMacs. Mini DVI connectors on Apple hardware are capable of carrying DVI, VGA, or TV signals through the use of adapters, detected with EDID (Extended display identification data) via DDC. 

Mini VGA:  Mini-VGA is a non-standard, proprietary alternative used on some laptops and other systems in place of the standard VGA connector, although most laptops use a standard VGA connector. Mini-VGA connectors are most commonly seen on Apple’s iBooks, eMacs, early PowerBooks (12 inch), and some iMacs (e.g. the iMac G5), but have also been included on several laptops manufactured by Sony. Apart from its compact form, mini-VGA ports have the added ability to output both composite and S-Video in addition to VGA signals through the use of EDID. The mini-DVI and now Mini DisplayPort connectors have largely replaced mini-VGA.

Apple Hi-Density Video HDI-45:  The HDI-45 connector was one of Apple Computer’s proprietary cable-to-onboard video connectors. It is a 45-pin connector that stands for High-Density Interconnect 1. The HDI-45 was used only in the first generation Power Macintosh computers (the Power Macintosh 6100, 7100, and 8100), specifically connecting these computers to the Apple AudioVision 14 Display, the only display to use this connector.

Apple Display Connector – ADC:  The Apple Display Connector (ADC) is a proprietary modification of the DVI connector developed by Apple in 1998. It combines analog and digital video signals, USB, and power all in one cable. The ADC connector has 35 pins arranged in a single row, and it was used in later versions of the Apple Studio Display and most versions of the widescreen Apple Cinema Display. The ADC connector was superseded by DVI in June 2004 1. The Apple DVI to ADC Adapter was introduced to allow ADC monitors to be used with DVI-based machines.

LFH-60 (Dual DVI-D):  The LFH-60 connector is a type of electrical connector that is used to connect a video source to two DVI-I monitors. It is also known as Low-force helix connector. The LFH-60 connector has 60 pins arranged in two rows of 30 pins each. The LFH-60 connector is used in some Matrox products, such as the G200/G450 Multi-Monitor Series, Millennium G550 Dual DVI, Millennium G550 Low-profile PCI, Millennium P650 LP PCIe 128, Millennium P650 Low-profile PCI, QID AGP, and QID Pro. The LFH-60 connector is not compatible with standard DVI or VGA connectors, but it can be used with an adapter.

DMS59 (Dual DVI-D):  DMS59 (Dual DVI-D) is a 59-pin electrical connector that is generally used for computer video cards. It provides two Digital Visual Interface (DVI) or Video Graphics Array (VGA) outputs in a single connector. A Y-style breakout cable is needed for the transition from the DMS-59 output (digital + analog) to DVI (digital) or VGA (analog), and different types of adapter cables exist. The connector is four pins high and 15 pins wide, with a single pin missing from the bottom row, in a D-shaped shell, with thumbscrews. The DMS-59 connector is used by AMD (AMD FireMV), Nvidia, and Matrox for video cards sold in some Lenovo ThinkStation models, Viglen Genies and Omninos, Dell, HP, and Compaq computers. DMS-59 connectors also appeared on Sun Computers.

HDMI:  HDMI (High-Definition Multimedia Interface) is a proprietary audio/video interface for transmitting uncompressed video data and compressed or uncompressed digital audio data from an HDMI-compliant source device, such as a display controller, to a compatible computer monitor, video projector, digital television, or digital audio device. HDMI is found on TVs and other devices from a variety of manufacturers, including, but not limited to, those made by LG, Samsung, Panasonic, Sony, and Vizio. Devices that may incorporate HDMI connectivity include: HD and Ultra HD TVs, video and PC monitors, and video projectors. HDMI can support resolutions up to 2560×1600 (WQXGA) in its DisplayPort 1.1a implementation, and 4096×2160 (4K) in its DisplayPort 1.2 implementation. With an adapter, the Mini DisplayPort can drive display devices with VGA, DVI, or HDMI interfaces. 

Micro-DVI: The Micro-DVI is a proprietary video output port introduced on the original MacBook Air in 2008. It is smaller than the Mini-DVI port used by its MacBook models. To use the port for displaying video on a standard monitor or television, an adapter must be used. Both a Micro-DVI to DVI adapter and a Micro-DVI to VGA adapter were bundled with the original MacBook Air. A Micro-DVI to Video adapter, which provided composite and S-video outputs, was also sold separately. The Micro-DVI to DVI adapter is only compatible with a DVI-D (digital) signal; DVI-A and DVI-I signals do not work as they do not have the required analog connections. The Micro-DVI connector was replaced with the Mini DisplayPort connector starting with the Late 2008 MacBook Air, making it one of the shortest-lived connectors created by Apple.

Display Port:  DisplayPort (DP) is a digital display interface developed by a consortium of PC and chip manufacturers and standardized by the Video Electronics Standards Association (VESA). It is primarily used to connect a video source to a display device such as a computer monitor. It can also carry audio, USB, and other forms of data. DisplayPort was designed to replace VGA, FPD-Link, and Digital Visual Interface (DVI). It is backward compatible with other interfaces, such as HDMI and DVI, through the use of either active or passive adapters. DisplayPort is the first display interface to rely on packetized data transmission, a form of digital communication found in technologies such as Ethernet, USB, and PCI Express. It permits the use of internal and external display connections. Unlike legacy standards that transmit a clock signal with each output, its protocol is based on small data packets known as micro packets, which can embed the clock signal in the data stream, allowing higher resolution using fewer pins.

DVI Video:  DVI (Digital Visual Interface) is a video display interface that was developed by the Digital Display Working Group (DDWG) to replace VGA, FPD-Link, and Digital Visual Interface (DVI). It is used to connect a video source, such as a video display controller, to a display device, such as a computer monitor. DVI devices manufactured as DVI-I have support for analog connections and are compatible with the analog VGA interface 1 by including VGA pins, while DVI-D devices are digital-only. DVI can support resolutions up to 2560×1600 (WQXGA) in its DisplayPort 1.1a implementation, and 4096×2160 (4K) in its DisplayPort 1.2 implementation. DVI is predominantly associated with computers, but it is sometimes used in other consumer electronics such as television sets and DVD players.

DE-15/HD-15/VGA/SVGA:  DE-15, HD-15, VGA, and SVGA are all names for the same type of video connector. It is a 15-pin D-subminiature connector that is used to connect a video source, such as a computer, to a display device, such as a monitor or projector. The connector is sometimes referred to as a mini-sub D15. The VGA connector is a standard connector used for computer video output. Originating with the 1987 IBM PS/2 and its VGA graphics system, the 15-pin connector went on to become ubiquitous on PCs, as well as many monitors, projectors, and high-definition television sets. The VGA connector carries analog RGBHV (red, green, blue, horizontal sync, vertical sync) video signals. SVGA (Super Video Graphics Array) is a term used to describe a computer display standard that has a resolution of 800×600 pixels or higher.