Computer keyboard

• 1. Introduction

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  The computer keyboard borrowed its shape from a machine it was meant to outlive: the typewriter. Its keys act as mechanical levers or electronic switches, arranged into buttons that have stayed familiar for half a century. Since the 1970s, this teleprinter-style device has been the main way people put words into machines. The mouse arrived to help in the 1980s. The touchscreen joined in the 2000s. Yet the rows of keys persisted, and they persist still. Press one key and a single written symbol usually appears. But some symbols demand that several keys be held at once, or struck in sequence. Other keys command nothing onto the page at all. Behind every press sits a question the machine must answer: what did the finger actually mean? The story of how that question gets resolved runs from stock tickers and punch cards to lasers projected onto a tabletop, and to vans parked across the street, listening.

• 2. From Tickers To Terminals

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  In the 1870s, teleprinter-like devices were already typing and transmitting stock market text across telegraph lines. The data traveled to stock ticker machines, copied instantly onto ticker tape. From this lineage the keyboard drew its purpose as a tool for both typing and sending. The teleprinter took its more contemporary form between 1907 and 1910, built by the American mechanical engineer Charles Krum and his son Howard. The electrical engineer Frank Pearne made early contributions, and separate models came from Royal Earl House and Frederick G. Creed. A second ancestor entered through Herman Hollerith, who developed the first keypunch devices. By the 1930s those machines had grown keys for text and number entry much like an ordinary typewriter. Early computers fused these traditions directly. The ENIAC used a keypunch device as both its input and its paper-based output. The BINAC relied on an electromechanically controlled typewriter, writing data onto magnetic tape rather than paper and handling output as well. The keyboard would stay the most integrated peripheral of all until a new consumer device began to share its territory.

• 3. The Anatomy Of A Standard

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  Most full-size keyboards today follow one of three mechanical layouts: ISO, ANSI, and JIS. The names point to the standards bodies behind worldwide, United States, and Japanese specifications. ANSI standard alphanumeric keyboards place keys on three-quarter inch centers, 0.75 inches apart, with a key travel of at least 0.15 inches. A keyboard is counted by its total keys: 101, 104, 105, and so on, all sold as full-size. A US-convention board typically carries 104 keys, while the 105 key layout is the norm across the rest of the world. Designers skip keys for compactness or preference. The most common omission is the numpad, since the alphanumeric section can usually replace it, and such designs are called tenkeyless, or TKL. The shape of one key betrays the underlying standard. On ANSI keyboards the Enter key sits in a single row, while on ISO keyboards it spans two rows in an inverse L shape. A standard, though, is only a starting point, because the same keys can be bent, folded, and shrunk to fit very different hands and rooms.

• 4. Many Shapes For Many Hands

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  Laptop keyboards trade range for thinness, with a shorter travel distance and a reduced set of keys, often relocating the function keys. Their switch mechanism is more likely a scissor switch than a rubber dome, the opposite of the trend on full-size boards. Flexible keyboards sit between the two, taking a full key arrangement from desktops and a short key distance from laptops. Most are made from silicone, which makes them water- and dust-proof, a virtue in hospitals where keyboards face frequent washing. Handheld ergonomic keyboards are designed to be held like a game controller. They pack a standard board's letters and symbols into fewer keys, reached by pressing two sets at once, with one set acting like a Shift key for capitals. Some even fold in a trackball mouse. Thumb keyboards appeared for devices without a built-in one, used in personal digital assistants such as the Palm Treo and BlackBerry, and in Ultra-Mobile PCs such as the OQO. At the other extreme stand multifunctional keyboards, programmable boards that can control multiple PCs and workstations across multi-screen environments. They may carry biometric or smart card readers, trackballs, and even touchscreen displays to stream video or trip alarms. Their natural homes are the consoles of financial traders and the control rooms of emergency services and air traffic management.

• 5. Designing Against Pain

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  Klockenberg published a study in 1926 arguing that the primary key clusters for two-handed typists should split into left and right halves set at an angle, so the wrists could stay straight. The concern was real biomechanics: a conventional layout can force shoulder elevation, wrist ulnar deviation, and head rotation. The most relaxed typing position keeps the forearms parallel to the ground and the wrists held straight. A more detailed study followed in 1972 from Kroemer, suggesting an adjustable split keyboard could reduce a user's pain. During the 1970s, several studies warned that data entry operators risked musculoskeletal injuries. The danger named in the source is concrete. Any keyboard may cause carpal tunnel syndrome or other repetitive strain injury to the hands, wrists, arms, neck, or back. The defenses are mundane and physical. Take frequent short breaks to get up and walk around a couple of times every hour, vary tasks through the day, and keep the shoulders relaxed with the elbows at the side. The chair height and keyboard tray should be set so the wrists stay straight, and the source advises against resting wrists or palms on sharp table edges, or using wrist rests while typing. The most radical responses abandon the standard layout entirely.

• 6. Breaking The One Key Rule

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  Douglas Engelbart invented the first one-handed keyboard, a chorded keyboard, where actions attach to combinations of key presses rather than to single keys. Other one-handed designs include the FrogPad, the Half-keyboard, and one-handed Dvorak. Because so many combinations are available, a chorded keyboard can produce more actions from fewer keys. Court reporters' stenotype machines use exactly this idea, entering a whole syllable with each stroke rather than one letter at a time. As of 2007, the fastest typists used a stenograph, the chorded board favored by most court reporters and closed-caption reporters. The trade-off is steep, since proficiency demands practice and memorization of the combinations. Virtual keyboards take the opposite path, dropping physical keys altogether. They display an image of a keyboard on screen, operated by a mouse or a touchscreen, and they spread quickly on touchscreen cell phones because hardware keyboards cost money and space. Microsoft Windows, Mac OS X, and some varieties of Linux include such on-screen keyboards. Projection keyboards push the abstraction further, using a laser to throw an image of keys onto a flat surface. A camera or infrared sensor watches the fingers and counts a key as pressed when it sees a finger touch the projected image. The cost is real comfort, because the keys cannot be felt and users often report increased discomfort in their fingertips from the lack of give.

• 7. Inside The Switch

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  In the early 1970s, the first electronic keyboards used individual switches inserted into holes in metal frames, costing 80 to 120 USD and bound for mainframe data terminals. The most popular type was the reed switch, its contacts sealed in a vacuum inside a glass capsule and tripped by a magnet on the switch plunger. Lower-cost direct-contact switches arrived in the mid-1970s, rated for ten million cycles, a shorter life accepted because terminals were already living shorter lives. In 1978, Key Tronic Corporation introduced capacitive-based switches, among the first not to use self-contained switches, instead reading a change in capacitance as a plunger pad neared traces on the circuit board. Prices reached 60 dollars, and Key Tronic became the largest independent keyboard manufacturer. IBM took its own road with a patented buckling spring mechanism, in which a coil spring buckles under the finger and trips a hammer that presses two conductive membranes together, producing a click and physical feedback. The early electronic keyboards had a typewriter-like travel distance of 0.187 inches and stood about two inches thick, before the market settled on 0.110 inches of travel and Key Tronic introduced a board only about one inch thick. Durability shaped even the lettering, since legends must survive tens of millions of presses against fingers, fingernails, and hand oils. Engraving filled with paint was never acceptable, so makers used two-shot molding, then explored sublimation printing and laser engraving, the latter able to print a whole keyboard at once. Three final mechanical advances, the monoblock housing, contact-switch membrane sheets, and refined plastics, drove the cost well under 10 dollars.

• 8. What The Machine Hears

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  One test for whether a computer has crashed is to press the caps lock key, because a working machine answers by turning on the light. The keyboard itself contains control circuitry that converts presses into key codes, usually scancodes, the only information sent onward. The switches sit in an electrical X-Y matrix, scanned line by line to find which key closed. The first keyboard microprocessor arrived in 1972 from General Instruments, and from 1978 onward keyboards used the single-chip 8048 microcontroller. Two failures haunt cheaper designs. When a key is pressed, its contacts may bounce for several milliseconds, and without debouncing the computer would read many strokes for one. The second is rollover, the trouble that appears when several keys are down within the same milliseconds. Early solid-state and diode-equipped direct-contact boards offered n-key rollover, recognizing any number of simultaneous presses. Without isolation diodes, three pressed keys can summon a fourth phantom key at the intersection of their X and Y lines. The connection back to the system has its own history, from the AT connector to PS/2 and then USB, with Apple once using its proprietary Apple Desktop Bus. The 1984 Apricot Portable stands as an early example of an infrared keyboard. Wireless freedom carries a hidden cost the listener can take away from this device that seems so ordinary. Neal O'Farrell, executive director of the Identity Theft Council, recounted that more than 25 years ago, former spooks showed him how they could capture a user's ATM PIN from a van parked across the street, simply by capturing and decoding the electromagnetic signals generated by every keystroke.