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A keyboard is an input device which uses typewriter-type keys (called “keycaps”) to deliver text and commands to the computer. But they’re much more than that.
Keyboards come in various layouts (ABCDE, XPeRT, QWERTY, AZERTY, DVORAK, MIT), often named after the first keys in the pattern, also for the operating systems they control (i.e. Apple, PC, Unix, Linux, etc.)
Also, they come in various sizes and types (roll-up, backlit, ergonomic (see below), gaming, etc.).
In 1966, IBM extended the basic typewriter keyboard with the addition of function (“Fn”; click HERE to see what they’re about), arrow and control keys (“C TRL” & “CMD”) as well as other keys (home, end, delete, Alt, Esc, etc.) to create the “IBM Standard 101-Key” keyboard, which is still the predominant keyboard in use today. More recent Windows keyboards include the “Windows” key, as Apple has the “Apple” key and Linux the “Tux” and Meta keys, all of which shortcut menu functions within that specific operating
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Standard IBM-Style Keyboard
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system. Further, most keyboards have a number of “programmable” keys which can be added by users.
But, essentially, all keyboards work the same, although how they get there is slightly different. Every key is essentially a “switch” which, when depressed, completes a circuit. All of the switches for the keys are contained on what’s known as the “key matrix” which is the grid of circuits below the keys. The electrical impulse  created when the circuit is closed then communicates that particular function through a ROM chip on a circuit board on the physical keyboard known as the “character map,” which translates the electrical impulse and sends a command to the computer’s processor for the appropriate
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Keyboard microprocessor and controller circuitry, courtesy computer.howstuffworks.com
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responsive action. There are various technologies used for key switches. Most common today (because they’re cheaper) are the “membrane” type, which uses a circuit pattern printed onto a plastic sheet which completes the circuit when a key is pressed against it (see right). Before that, “mechanical” metal contact keyboards were quite popular. They actually had spring-loaded keys which used a metal strip at the bottom of a plunger to make the contact, sometimes with an audible “click”. Less frequently used now are rubber dome and foam element switches, as well as “capacitive” switchboards (which run a continuous current but detect changes in that current when keys
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Membrane type keyboard construction, courtesy wikipedia >
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are depressed), photo-optical (light sensitive), laser (projected), Hall-effect (magnetic), buckling spring and scissor switchs (different mechanical construction). For more explanation, click HERE.
Early on, some computers had a row of “dip switches,” which were used to adjust the keyboards (such as the OmniKey 101) to work with various computer configurations , but aside from refurbished ones, they’ve pretty much outlived their usefulness as the result of vast improvements in operating systems.
Moreover, keyboards may also be “virtual” (typing on a screen image like an iPad or smart phone), “island,” where all of the keys are separated by a continuous base or “deck” plate surrounding them, “chicklet,” where the beveled keys almost  touch each other (photo at left for those too young to remember), essentially a membrane keyboard with flat low-travel keys) or the standard mechanical (“IBM 101 Key”) version discussed above.
Lastly, keyboards have differing ways of communicating with the computer’s CPU, including physical connectors (e.g. DIN, PS-2 and USB) and wireless (e.g. Bluetooth, infrared) connections. For a more lengthy explanation, click HERE. Depending on the model (there have been about 13), Apple keyboards have special menu keys for CTRL, FN, Option, Alt, Apple, Power and CD/DVD eject. PC keyboards may have the CTRL, Alt and Microsoft keys, depending on the version of the keyboard. Sun Microsystems and Space-cadet (“MIT”) keyboards with the meta and “compose” keys are used with various Linux and Unix. All are used for menu shortcuts in combination with other keys. To confuse the issue slightly further , not all keyboards are straight and square. Ergonomic keyboards are shaped, it is claimed, to reduce wrist and finger fatigue.
I’ll bet you didn’t know there was that much to know about keyboards, did you?
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Microsoft Ergo Keyboard >
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