There are 26 letters in the English alphabet with two symbols for each, as lowercase and uppercase letters. Though capital letters have typically been printed on the keys themselves, the keys have inserted lowercase letters by default. A shift key has been typically used for accessing the capital letters by pressing it before typing a letter, then letting go of the shift key when done typing capital letters.
The shift key has been used for inserting the symbols on the top half of keys with numbers and punctuation, too. Therefore, the capital letters have been implied to be the top half of the letter keys, even though the lowercase letters have not been present simultaneously.
There has been a caps lock key for toggling the shift effect by typing it rather than having to hold the shift key itself, though that has been implemented inconsistently. While capital letters are always produced by the letter keys when the caps lock key is in effect, some software will ignore it for keys without letters, as would be expected by the term "caps". However, some other software will treat it like a shift lock instead, and produce the symbols from the top half of the other keys, too. Of course, some keyboards have an aptly named shift lock key instead.
Additionally, the shift key has been used for marking text as the selection. The shift key is pressed and then either a cursor within the text is repositioned with movement keys, or a pointer floating over the text is loosely coordinated to indicate the beginning and ending of the desired selection. The selected text can then be removed, or copied and then deselected.
There are ten digits for numbers: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9. On a typical keyboard there has been about 32 symbols and punctuation. The punctuation has shared keys with the numbers in a similar manner as lowercase and uppercase letters, though rarely with any obvious relationship. This pairing has typically resulted in 21 keys for numbers and punctuation, with the aformentioned shift key having been used to access the other half of the pair.
Thirty-six keys for letters and symbols. Additional modifier keys for computer use.
A compact version of the functional keyboard with only twenty-four keys for letters and symbols, four per key. (Layout is complete, though description is yet to be revised.)
These are basic descriptions of keys for typing characters and symbols, without mentioning modifier keys or other keys for computer use. The 8-key keyboard labels the keys with the characters that will be produced from typing. The others are probably just geeky keyboards.
Note that ASCII (and therefore Unicode) defines everything typable from a typical computer keyboard. For example, the delete character is, in fact, a character, therefore there is no need for a delete key with either the chorded or the bit keyboards. The same can be said for space, newline, tab, and so forth. Though, it might be convenient to have a repeat key on any of these keyboards to repeat the last character entered.
Chorded keyboards require all necessary keys are pressed before releasing any of them, then they must all be released before typing another chord. This is forgiving by not requiring simultaneous key presses or key releases. Keys for a chord are usually grouped into no more than four keys, typically for typing the four bits of a hexadecimal value. Keyboards for non-chorded bit sequences would likely have a light by each key to indicate when it has been toggled as the value of one, for feedback and forgiveness.
Another possible approach is having the software interpret (perhaps when using a toggle switch or key on the keyboard) the bit sequence or hexadecimal values as typed from right to left, as an alternate means of skipping the leftmost zeros, especially when using any pausing of sequence entry as an indicator the sequence is complete. Though, pausing would likely be unsuitable or unnecessary with the non-chorded keyboards, and only suitable after releasing all keys of a chord.
A possible feature is a toggle switch (or key) that allows typing the inverse of the value for character. In other words, the bit mask for any character. For example, the delete character is seven bits of the value one: 1111111. With the switch active, the delete character could be entered a seven zeros. For this example of the delete character, this would mean faster key presses with the 1-bit keyboard, or simply using the zero key (and only once, rather then seven times) with the chorded keyboards.
Eight keys with twelve characters on each key provides room for 96 characters, enough for the 94 charcters of the US keyboard plus the space and newline characters if desired. Each key has three rows of four characters. Top row and left column are primary, so there are two modifier keys for the other two rows and three modifier keys for the other three columns. No more than two modifer keys are held, one for the column and one for the row, before typing a key.
Four keys for each hand. Five modifier keys managed by the thumbs, with the two row keys for the left thumb and the three column keys for the right thumb.
Seven keys representing 1, 2, 4, 8, 16, 32, and 64. There would be a thumb key for zero, only useful for the null character. Keys are chorded, so all necessary keys are pressed before any are released. The sum of the values represented by the keys is the ASCII value for the desired character. Notably reminiscent of a braille keyboard.
This is usable with ASCII or Unicode, or whatever. Two keys with values representing 0 and 1 are used to type the binary value of the character. Either the whole binary number can be required for automatic interpretation of characters, or a character insert key can be used to allow for skipping the initial zeros.
A single key is pressed for a short period of time or a long period of time, and then released. The former is interpreted as the value zero and the latter as the value one. This is reminiscent of typing morse code. The time in between key presses is ignored, which makes it forgiving.
Two lights could be used for feedback: one light would immediate turn on when the key is pressed to indicate the zero value, and then after holding the key for a moment that light turns off and other light turns on to indicate the value of one. Or both lights can remain on to indicate one. Or a single light that changes color depending on how long the key was pressed. Either way, the light turns off after releasing the key.
A character could be entered automatically after seven key presses for ASCII, or sixteen key presses for Unicode, depending on the software interpreting it. An alternative would be to have the computer interpret the first key press as the rightmost digit and last key press as the leftmost digit, then the leftmost zeros can be left off and the character would be interpreted after a short amount of time of not typing the key at all. Or use a character insert key after typing the sequence to indicate when to interpret it.
Sixteen keys in two rows of two groups. Each group has four keys representing 1, 2, 4, and 8. Each group is chorded, so all necessary keys for the sum of a hexadcimal value are pressed before being released. The top row are the two leftmost hexadecimal digits of a Unicode character, and the bottom row are the two rightmost digits. A zero key is available for the right thumb for when the rightmost hexadecimal value is zero, otherwise it is unused.
Each hexidecimal value is entered one at a time starting with the top left group and ending with the bottom right, one group at a time. Leftmost zeros are skipped rather than entered, quickening entry. The full hexadecimal value is considered to be entered when the bottom right group of keys (or the zero key) are released.
One key for each bit. In other words, a key representing each value: 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768. If labeled at all, probably just as 1–16. However, for feedback and forgiveness a light for each key could be lit to indicate bits that will be interpreted as the value one, and would toggle off when typed again. A character insert key is used to indicate the sequence is complete, so technically the bit keys could be typed in any order. An additional key for zero could be used for the null character, or perhaps type the character insert key without typing anything beforehand.
This is a compact version of the 16-bit chorded keyboard, with essentially only the bottom row of keys and the zero key. There is also a character insert key that is typed when all the hexadecimal values have been entered. Similar to the 16-bit keyboard, leftmost zeros can be skipped.
This is a compact version of the 16-bit and 8-bit chorded keyboards. There are only 6 keys: one group of four keys for typing a hexadecimal value, a zero key for the final hexadecimal value when needed, and a character insert key.
Sixteen keys, two rows of eight keys, representing each hexadecimal digit from zero to fifteen, likely having the unfortunate combination of numbers and letters commonly used for hexadecimal. Simliar to the 8-bit and 4-bit keyboards, a character insert key enables bypassing entering leftmost zeros, Notably, no chording of keys.