title: How do event triggers affect program flow?
body: <p>If my program is in the middle of doing some operation in Function A and a timer tick event is triggered that calls Function B, what happens to my program flow? Does it immediately stop what is happening in A and jumps to B? If so, does it return eventually to where it was in A? Does it finish A first, then go to B? Does it do each on a separate thread? Something else entirely?</p>
  
  <p>I want to use a timer for something, but my understanding of the way it works makes it seem like it can wreak havoc with a program's predictable control flow. Am I mistaken?</p>