The problem with delay() is that your code is stuck waiting for the time to elapse. What if you wanted to do something more in that time? There are places where you don’t need to do anything with your processor resource but more often then not, you need to be doing something useful. The IsTime() function introduced lets you use all that time to do more things.
This is the first of two related articles. First we discuss the limitations associated with using delay() type functions and introduces the IsTime() solution. The second article will introduce the PolledTimer library which simplifies things even more.