Imagine a cruise control in a car. Let's say that speed is measured (this may be the way it is really done, but it is speculation) by monitoring a point on the wheel and every time it passes the vertical a subroutine runs that calculates the time difference by using the system clock time now and the last time the subroutine ran and then the speed by dividing the circumference of the wheel by the time difference.
If on two runs, the system clock reports the same time, I can think of two possibilities:
- the system clock is broken
- the wheel is rotating so fast that the system clock does not have enough resolution.
Would you prefer the subroutine to report the speed as 0 thereby causing the cruise control to put the pedal to the metal; "really really fast" thereby causing the cruise control to slam on the breaks, or at least cut all power; or "I don't know how fast we are going" thereby causing the cruise control to disengage, perhaps with a warning to the human driver?