Why are some keyboards able to register three inputs at once, while others can only manage two?
In: Technology
A keyboard have far too many keys for each key to have their own sensor. It would just be too many wires and sensors to manage. Instead the switches on the keyboard are mounted in a grid matrix of wires where they connect the row and column wires together when pressed. The controller will activate a pattern of columns and observe the signals on the rows to figure out which keys are pressed. The issue is that if you press too many keys there is just too many rows that activates as all the wires gets connected together and there is no way to figure out which keys are actually pressed. Identifying two distinct keys is already a challenge and requires some interpretation of the signals. Identifying three distinct key presses is almost impossible unless you put resources into solving the issue. Some keyboards do allow three button presses as long as they are common patterns as they are able to arange those keys on the matrix in a way that makes it possible to distinguish them. Others allow three buttons as long as some of the buttons are control keys which may have extra hardware on them to make them easier to distinguish. Other keyboards will add extra hardware to the keyboard to make sure all keys can still be distinguished from each other even though this increases the cost of the keyboard significantly.
Keyboards have tiny memory in them. Every key on the board has a special number. Whenever a confirmed key press occurs, this number stored in this memory and is sent to the computer. Your OS (Windows, MacOSX, etc) have a special database called keymaps. They refer these numbers from keyboards and translate it as various things.
Now, the cheap keyboard manufacturers know most popular combination of keystrokes. Like CTRL+C, CTRL+ALT+DEL, CTRL+V, etc. They have special numbers for these too. But some expensive keyboards have larger memories on-board and sometimes even have specialised software that can retrieve these keystrokes and process them.
That’s why you see that some keyboards are able to send multiple keystrokes while some can’t.
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