peripheral device
An electronic device that is outside the computer's system unit (external to the computer's enclosing case), but used by the computer to which it is connected, such as a printer or a scanner.
peripheral device: gear bolted outside the main box
A peripheral device is any hardware that sits outside the computer's main enclosure but communicates with it to perform work. The printer on your desk, the scanner on the bench, the barcode reader mounted at a station, the industrial camera watching a production line: these are all peripherals. They extend what the core machine can do, but they live separately from the CPU, memory, and control boards inside the case.
Peripherals connect through standardized ports and protocols. USB is the modern workhorse for office equipment and light industrial use. Serial RS-232 connections still handle legacy instruments and process sensors in factories. Ethernet links network printers, cameras, and data collection boxes across an operation. Some industrial peripherals use parallel printer ports, SCSI, or vendor-specific connections. The key difference is distance: a peripheral can sit meters away from the computer, or even on another continent if networked.
Input, output, and storage peripherals
Input peripherals feed data into the system: keyboards, mice, barcode scanners, weight scales, machine sensors, card readers, vision systems. Output peripherals take data from the computer and make it physical: printers, displays, LED indicators, buzzer units, pneumatic valve drivers. Storage peripherals hold files: external hard drives, tape backup units, USB flash drives. Some peripherals do double duty, like networked storage that both sends and receives.
The industrial world uses peripherals differently than office environments. A factory computer might drive an industrial printer that marks parts at 10 meters per minute. A process controller talks to temperature sensors, pressure gauges, and flow meters scattered around a plant floor. Vision systems and encoders feed images and motion data back to the main processor. These devices often work in hot, wet, or dusty settings, so they use ruggedized connectors and metal housings rather than plastic desktop gear.
Failure points are frequent. Cables wear out from movement or vibration. Drivers become obsolete when operating systems update. Protocol mismatches occur when old equipment meets new computers. Power delivery can fail if a single supply feeds too many devices. In production environments, losing a peripheral can stop a line: a broken printer means no labels, a failed sensor means no feedback, a bad network connection means lost data. This is why industrial shops often stock spares and keep older computers running longer than office workers would tolerate.