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A peripheral device is an internal or external device that connects directly to a computer or other digital device but does not contribute to the computer's primary function, such as computing. It helps end users access and use the functionalities of a computer.
Since it’s not a core device for the system, the computer can still function without the peripheral, which simply provides extra functions. However, some peripherals such as a mouse, keyboard, or monitor tend to be pretty much fundamental to the interaction between the user and the computer itself.
A peripheral device is also called a peripheral, computer peripheral, input-output device, or I/O device.
A peripheral device provides input/output (I/O) functions for a computer and serves as an auxiliary computer device without computing-intensive functionality. Peripheral devices connect with a computer through several I/O interfaces, such as communications (COM), Universal Serial Bus (USB) and serial ports such as serial advanced technology attachment (SATA) ones.
Peripheral devices include the following:
There are several types of peripherals, although they’re commonly divided into three broad categories: input, output, and storage devices.
Input devices convert incoming instructions or actions from the user into viable information that can be interpreted by the computer. For example, a keyboard will convert keystroke into characters that appear on the computer’s display, while a monitor will transform hand movements into movements of a cursor that can be used to interact with the operating system’s programs. Other input peripherals include joysticks, microphones, webcams, optical scanners, etc.
Output peripherals translate digital signals into information that can be interpreted or utilized by the end user. For example, a monitor or display screen will show the operating system’s desktop, while a laser printer will translate information saved in a word file into printed material. Other output peripherals include speakers, 3D printers, and projectors.
Some devices can provide both input and output signals, such as network interfaces, modems, routers, and webcams.
Storage peripherals are used to store and record data, and include internal and external hard drives, CD-ROM and DVD drives, and flash memory drives.
Depending on whether the peripheral is located inside or outside the computer system case, it can be further classified as an internal or external peripheral device.
An external peripheral can be connected via many different types of cables and connections. Today, the most common connection for external peripherals is the USB connection, both because most computers have several ports available, and because of the simplicity of the plug-and-play feature.
Internal storage devices such as hard disks are usually connected with a SATA cable, while display port and HDMI are the most popular connections for displays and monitors.
Today, many peripherals are built-in inside smaller computer devices such as tablets, laptops and smartphones. For example, webcam, speakers and microphones are integrated inside most smartphones, although the latter cannot be considered a peripheral since it’s a core function of any phone. Similarly, webcams and monitors are integrated into most laptops, although it’s still possible to connect the computer to a larger monitor or higher resolution webcam.