A peripheral is a device attached to a host computer, but not part of it, and is more or less dependent on the host. It expands the host's capabilities, but does not form part of the core computer architecture

Computer architecture

In computer science and engineering, computer architecture is the practical art of selecting and interconnecting hardware components to create computers that meet functional, performance and cost goals and the formal modelling of those systems....

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Examples are computer printer

Computer printer

In computing, a printer is a peripheral which produces a text or graphics of documents stored in electronic form, usually on physical print media such as paper or transparencies. Many printers are primarily used as local peripherals, and are attached by a printer cable or, in most new printers, a...

s, image scanner

Image scanner

In computing, an image scanner—often abbreviated to just scanner—is a device that optically scans images, printed text, handwriting, or an object, and converts it to a digital image. Common examples found in offices are variations of the desktop scanner where the document is placed on a glass...

s, tape drive

Tape drive

A tape drive is a data storage device that reads and performs digital recording, writes data on a magnetic tape. Magnetic tape data storage is typically used for offline, archival data storage. Tape media generally has a favorable unit cost and long archival stability.A tape drive provides...

s, microphone

Microphone

A microphone is an acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1877, Emile Berliner invented the first microphone used as a telephone voice transmitter...

s, loudspeaker

Loudspeaker

A loudspeaker is an electroacoustic transducer that produces sound in response to an electrical audio signal input. Non-electrical loudspeakers were developed as accessories to telephone systems, but electronic amplification by vacuum tube made loudspeakers more generally useful...

s, webcam

Webcam

A webcam is a video camera that feeds its images in real time to a computer or computer network, often via USB, ethernet, or Wi-Fi.Their most popular use is the establishment of video links, permitting computers to act as videophones or videoconference stations. This common use as a video camera...

s, and digital camera

Digital camera

A digital camera is a camera that takes video or still photographs, or both, digitally by recording images via an electronic image sensor. It is the main device used in the field of digital photography...

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Common peripherals

• Storage
  Computer storage
  Computer data storage, often called storage or memory, refers to computer components and recording media that retain digital data. Data storage is one of the core functions and fundamental components of computers....
  
  
• Input
  Input/output
  In computing, input/output, or I/O, refers to the communication between an information processing system , and the outside world, possibly a human, or another information processing system. Inputs are the signals or data received by the system, and outputs are the signals or data sent from it...
  
  
  • Input device
    Input device
    In computing, an input device is any peripheral used to provide data and control signals to an information processing system such as a computer or other information appliance...
    
    
• Output
  Output
  Output is the term denoting either an exit or changes which exit a system and which activate/modify a process. It is an abstract concept, used in the modeling, system design and system exploitation.-In control theory:...
  
  
  • Output device
    Output device
    An output device is any piece of computer hardware equipment used to communicate the results of data processing carried out by an information processing system to the outside world....
    
    
  • Display device
    Display device
    A display device is an output device for presentation of information in visual or tactile form...
    
    
  • Graphical output device
  • Computer display
    Computer display
    A monitor or display is an electronic visual display for computers. The monitor comprises the display device, circuitry, and an enclosure...
    
    

A device such as keyboards, printers, or even your computer monitors are known as Peripheral Devices. Peripheral devices connect to the system unit through the ports on the computer.