Keyboards were in the computer world before the appearance of the first personal computers, since they were used in the terminals of minicomputers. Have you ever wondered how the PC can tell which key on the keyboard you pressed? It’s something simple, but in case you’ve ever been curious, we’ll explain it to you.
The keyboard is arguably the oldest input device in computers, it has been used since before the appearance of the mouse and is still in use today. However, it hasn’t changed much since.
Keyboards precede the PC
At the end of the 60s, the first terminals appeared, it was a keyboard and a screen that were remotely connected to a large computer in the same room. A comparison today would be when we are running a remote application in the cloud.
These terminals did not use complex graphics systems, but their environments were purely textual, but required a keyboard for entering commands, which were visible on the screen in front of the user. The terminals were not processing anything and the room computer only processed the written code or the list of commands when the Enter key was pressed on the keyboard.
So in the terminal there was a process that showed every character on the screen in real time, the character sample was not performed using some kind of processing in the medium.
How the keyboard detects the pressed key
In fact, it is the keyboard itself that detects which key we pressed, in each keyboard there is a circuit matrix where each key is connected to a matrix of cables. From which row and column of the matrix is active at any time, the keyboard sends one code or another, each different code corresponding to a specific character.
In early terminals and early personal computers, this code was the memory address in a character ROM. Hence the character was selected and that same ROM sent the previously stored character to the video output. The problem with this method? It was not possible to change the font or the size of the characters.
As PCs got more complex, they stopped using simple character ROMs and started using a bunch of fonts in different sizes and styles. This was mainly possible thanks to the increased capabilities of VRAM, but the system used remains the same as at the time and has not evolved.
Of course, keyboards now usually have a small internal memory that stores the last keys pressed and, in most cases, prevents blind keystrokes from accidentally reaching the screen. They are therefore a little more advanced than those of yesteryear, but it is a device that has hardly changed since.
