How to check if a key is pressed on a keyboard connected to Arduino?

Question

Arduino

You need to check the key hold on the Arduino matrix keyboard.
If the key is pressed, some action is performed.

Answer 1

What is "clamping" - this means that the key is pressed and not released for a certain time. This is what needs to be checked. When a press is detected, flag "key pressed" and remember the time. On subsequent checks of the keyboard status, do the following. If the key is released, then reset the flag. If the key is still pressed, then check if the specified time has passed. And either perform the action or wait further.