dhenry:
Is it possible to end a program forcefully?
Unplug this thing from power usually does it,
In a real mcu environment, you actually have the ability to led the code end and typically you restart from the beginning (making it effective a loop with setup()). In the arduino environment, you don't have that option right away, but you can manually edit the generated cpp file and perform make on your own.
Well you certainly can within a sketch enable the watch dog timer (WDT) to time out and interrupt in just 25 millisec if you wish, which will effect a reset to the chip just as if you hit the reset switch or cycled the power off and on.
Lefty