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A special piece of circuitry that is fitted inside a computer and sits between the computer and the port is called interface. The purpose of an interface is to provide a compatible connection between computer and port where the peripheral devices are connected.

A place where data can pass into or out of a central processing unit, computer, or peripheral is called port.




There are two types of interfaces. They are:

  • Serial interface
  • Parallel interface

Serial Interface

The serial interface is an interface which transfers one bit of data at a time. In a serial interface, only one line or a pair of lines are used to transmit a data. It is used for low-speed peripherals. Normally, serial interface is found in 9 pins. In the serial interface, data is transferred serially. So, the speed is slow.

Parallel Interface

The interface which transfers set of a bit at a time is called parallel interface. In a parallel interface, there are multiple lines to connect the peripheral to the port. A parallel interface is used to transfer data at a faster rate for high-speed peripherals such as a printer; disk and tape.

A parallel interface is also known as Centronics interface as it was first popularized for interfacing printers manufactured by Centronics. In parallel interface, data is transferred in parallelly. So, speed is high.

A port is a socket on the outside of the system unit that is connected to an expansion board on the inside of the system unit. A port allows connecting a peripheral device such as a monitor, printer, or modem so that it can communicate with the computer system.

Port is defined as a connection point on a computer where we can connect a device that passes data in and out of a computer. For example- a printer is typically connected to a parallel port (also called LPT port), and a modem is typically connected to a serial port (also called a COM port (COM1, COM2)).


  1. Ports are the connecting peripheral devices.
  2. Ports are used to transmit data to and from peripheral devices.
  3. It provides electrical power to those devices having low power requirement such as a mouse, keyboard, pen drive, etc.

Some of the popular communication ports are given below:

  • Parallel port

A parallel port allows lines to be connected that will enable 8 bits to be transferred simultaneously, like cars on an eight lane highway. It moves information faster than the serial lines.



It can be used to transfer data efficiently only up to 15 feet. Thus, parallel ports are used principally for faster speed devices such as connecting printers.

  • Serial Port

A serial port enables a line to be connected that will send bits one after the other on the single line, like cars on a one lane highway. Serial lines are used to link slow speed devices and equipment that is not close by.



It is also known as an RS-232 port. Serial ports are used principally for communications lines, modems and mice. They are frequently labeled COM for communications purpose.

  • Universal Serial Bus (USB)

Universal Serial Bus (USB) is a serial bus standard to connect devices to a host computer. It was designed to allow many peripherals to be connected using a single standardized interfaces socket, to improve plug and play capabilities that allows devices to get connected and disconnected without powering off the computer.

It includes providing power to low-consumption devices eliminating the need for an external power supply and allowing many devices to be used without requiring manufacture-specific drivers to be installed.



USB is used to connect computer peripheral devices such as a mouse, keyboard, gamepad, joystick, scanner, digital camera, printer, personal media player, flash drive, external drive, etc. For many of those devices, USB has been a great medium of connecting to a computer.

The USB 1.0 was introduced in 1994 and created by the core group of companies that consisted of Intel, Compaq, Microsoft, Digital, IBM and Northern Telecom. The USB 2.0 specification was released in 2000 and was standardized by the USB-IF in 2001. Again, USB 3.0 specification was released on 2008 by Promoter Group. Its transfer rate was up to 10 times faster than the USB2.0 version and has been dubbed the Super –speed USB.

  • IEEE 1394 Interface (Firewire port)

The IEEE 1394 interface is a serial bus interface standard for high-speed communication and isochronous real-time data transfer, frequently used by the personal computer as well as in digital audio, digital video and aeronautics applications.

Source: IEEE 1394 Interface (Firewire port)
Source: IEEE 1394 Interface (Firewire port)

It replaced parallel SCSI in many applications because of lower implementation cost and a simple more adaptable cabling system in the computer system.

  • SCSI port

SCSI port provides an interface for transferring data at high speeds for up to eight SCSI-compatible devices. These devices include external hard disk drives, magnetic tape backup units and the CD-ROM drives.


SCSI port pronounced “scuzzy” and short for small computer system interface.

  • Peripheral Component Interconnect (PCI Slot)

Peripheral Component Interconnect (often shortened to PCI) is a computer bus for attaching hardware devices in a computer. These devices can take the form of an integrated circuit fitted on the motherboard itself.



PCI specification or an expansion card, that fits into a socket PCI slots in PC helps to connect devices like network cards, sound cards, internal modems, etc.

(Shrestha, Manandhar and Roshan)


Shrestha, Prachanda Ram, et al. Computer Essentials. Kathmandu: Asmita's Publication, 2014.

  • Ports are the connecting peripheral devices.
  • Ports us used to transmit data to and from peripheral devices.
  • It provides electrical power to those devices having low power requirement such as a mouse, keyboard, pen drive etc.
  • Here are the some of the interface and ports that are used in computer system they are:
  1. Parallel port
  2. Serial port
  3. Universal Serial Bus
  4. IEEE 1394 Interface(Fire wire port)
  5. SCSI port
  6. Peripheral Component Interconnect (PCI Slot)




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