i have a schematic of running led (image on attached file),
on that project, LED will light on from 1st led, one by one ,until it reach the last led, and repeated from 16 to 1.
My homework is, make all 16 LED's Light on (together) when it reach the last led. how can i make it possible?
please tell me some clues.

 

You're going to have to add a wired-OR circuit to each LED and trigger its on state when LED16 goes active. Try using a diode for the wired-OR.

A wired-OR allows you to control your LEDs with two different circuits. That's your clue.

 

And you'll need a current limiting resistor on each LED. Or else they will be really dim when all of them are switched on at the same time.