- Keycap: Plastic outer covering of a particular key typically inscribed with the character that gets sent to the computer when struck.
- PCB: Printed Circuit Board (really, just a circuit board), which registers keystrokes and sends them to the computer.
- Switch: underlying mechanism that the keycap covers, and in some way creates contact with the PCB to let it know that a keystroke needs registering.
- Rubber Dome / Membrane: refers to a soft, flexible dome covering the PCB and under a keycap. Activation of the key happens when you fully depress the switch to the PCB to close a circuit, called bottoming out.
- Mechanical (Switch): Typically a more complex switch than a rubber dome, composed of a spring, a stem, and a housing, as the stem gets lowered by a keypress, two metal plates (called leaves) are made to come into contact with one another that close a circuit and indicate that a keypress has happened to the PCB. This design means that bottoming out isn't typically necessary, due to the leaves being allowed to come into contact at any point in the travel down. It also permits the modification of any part to change the characteristics and feel of the switch itself. For example, one could add more resistant springs under the home row and spacebar keys, and lighter ones in the keys activated by weaker fingers. These switches allow for a huge variety of customizations, which makes them both comparatively more rare and expensive. Another downside of mechanical switches is that they are by and large clones of Cherry MX switches. A company named Cherry had a patent for switches they created throughout the 80s. It expired some years ago and other companies simply started making clones, creating near uniformity in the physical dimensions of the switch. This means that creating variations here is still limited by this size. Nevertheless, that same uniformity does create a diverse market and a highly modular platform on which to build.
Most commercially available keyboards are Rubber Dome / Membrane Keyboards, for example, all the inexpensive Microsoft, Logitech, Dell, and even Apple keyboards use this design. They are less expensive to manufacture and are typically available in only two common designs, full size and 75%.
Most membrane keyboards are Full Size, meaning they have 104 keys, and have the keys laid out in a conventional, typewriter-inspired, row-staggered layout. It will have alpha, number, and modifier keys, a number pad, F-keys across the top, and a separate navigation cluser where you'd find arrow keys, PageUp, PageDn, etc. However, laptop popularity has allowed a more compact form factor to also become common, what's usually called a 75% layout, one that has all alpha and number keys, arrow keys that have been pushed into the main group, and maybe a handful of nav cluster keys, like PageUp, PageDn, etc. The Apple Magic Keyboard is an excellent example of this, and will serve as a good point of comparison.
Any missing keys, including arrows, nav cluster and even media control keys on
smaller form factors that omit those keys are going to be made available on
another layer, meaning you hold down some key (usually Fn) and some other key
to activate it.
After the Full size, the images of the other keyboards are overlaid over a full size for easier comparison. I made each of the subsequent images slightly transparent so it's possible to see when keys match standard full size key placement, and when they don't.
What we've all known and loved since the 80s.
Short for TenKeyLess (a weird name since it removes 17 keys), it's the first step in space-saving: just chopping off the numpad.
A big step towards compact-ness: No num pad, no nav cluster, but kept arrow keys and some of the buttons from the nav cluster, and all alphas, modifiers (Shift, CapsLock, Tab, Backspace, Enter), number keys, and F-row. Called such because it has about 75% as many keys as a full size. Matches the Apple Magic Keyboard in layout closely.
Slightly more compact than a 75%, by chopping off the F-row (and a personal
favorite). Of note here, and the biggest change from the 75% is that the
Escape button has been moved to where the tilde/backtick (~ ` ) normally
goes. As a longtime Mac user, this tends to bother me, and I move Escape to
CapsLock and move the tilde back to where it conventionally is (to the left of
1 !) on these (more on this later).
As compact as most people tend to go. This really is simply the full size center
group: no numpad, no F-row, no nav cluser, but also no arrow keys that require
changing the right shift button. In this illustration, the tilde is back again
in the top right, but most will put Escape there (again - more on this in a
later post).
Standard office fare, but also a typical laptop keyboard. It's also noteworthy that they're able to fit so much into a relatively small space, very nearly a 75% layout in almost the same physical size of a 60%. Because they're rubber dome, they are free to create switches and keycaps that can be more compact, and so may be worthy of consideration. The other form factors here typically only come in Mechanical switches.
