How to transfer signals between arduino?

Question

Arduino

there is a task to simply give a signal to another arduino so that the subsequent code is executed on it, how is this the easiest way to do it?
Due to the numerous hello world lessons from LEDs, it is very difficult to find a solution (

Answer 1

Try connecting an LED and a button.
For example so.
Blue pull-up - no signal digitalRead(A0) will return HIGH, green pull-up will return LOW.

Answer 2

Connect two arduins with digital pins (you can use an optocoupler for galvanic isolation). One for the output, the second for the input, and on one set a high level when the condition is met - and on the second, catch a high-level event at the corresponding input, and execute the corresponding code