Peripheral

Lore & Background

One of the earliest known computer peripherals was the punched card, introduced into computing in the late 1880s by American engineer Herman Hollerith. The punched card tabulator, the first computer peripheral to be mass-produced, could read the cards. In 1901, the punched card led to the Hollerith Type 001 Mechanical Card Punch, which became the basis of computer keyboards, allowing operators to punch digits 0-9 without knowing the corresponding card codes. Punched tape later replaced punched cards due to lower cost and higher storage capacity; the first documented computer to use punched tape as storage was the Zuse Z1 in 1938, which read source code on punched tape.

In the early 1950s, the UNISERVO I, created for the UNIVAC I computer, became the first commercially available magnetic tape drive, capable of both reading and writing to magnetic tape. In 1956, the IBM 305 RAMAC was the first commercial computer to ship with a hard disk, the IBM Model 350, which stored 5 MB on fifty double-sided magnetic disks 24 inches in diameter spinning at 1200 RPM. The RS-232 standard was developed in the early 1960s by the Electronic Industries Association to allow reliable serial connections between devices from different manufacturers using a D25 connector.

Personal computers became widespread from the 1970s onward, and existing peripherals such as keyboards and mice became standard, while new peripherals like scanners and webcams began development. IBM began using semiconductor memory in 1970, which could store twice as much data as core memory, and flash memory was invented in 1984.

Reader's Guide

Peripherals are categorized by the direction of information flow relative to the computer: input, output, or storage. Input devices convert incoming data (user instructions or environmental information such as temperature or pressure) into binary code expressed through electrical signals. They can be categorized by modality of output (e.g., mechanical motion, audio, visual), whether output is discrete (e.g., key press) or continuous (e.g., mouse position), and the number of degrees of freedom (e.g., two-dimensional mice or three-dimensional navigators for CAD). Examples include mouse, keyboard, scanner, game controller, microphone, and webcam.

Output devices reverse the process, turning binary code into comprehensible input for a user. The most common form is a display device, which presents output visually on a screen; the output appears temporarily and can be easily altered or erased. Display devices form images by illuminating a desired configuration of a two-dimensional matrix with rows and columns, refreshed many times per second (typically 60, 75, 120, or 144 Hz on consumer devices). Other examples include monitor, printer, headphones, and speakers.

Many external storage devices double as input/output devices, as they store information and also need facilities for loading information on and off memory (input) and showing the user what is being stored (output). Examples include disk drives, solid-state drives, USB flash drives, memory cards, tape drives, modems, routers, gateways, and network adapters.

Did You Know?

• The punched card tabulator was the first computer peripheral to be mass-produced.
• The Hollerith Type 001 Mechanical Card Punch, introduced in 1901, became the basis of computer keyboards.
• The IBM Model 350 hard disk, released in 1956, stored 5 MB using fifty 24-inch magnetic disks.

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