Interval

This program demonstrates periodic execution of tasks using the interval call.

Task 2 and Task 3 both run at 500Msec intervals.

Task 2 and task 3 are created by task 1. Task 3 is created 250Msec after task 2

The interval os call is a way schedule task to run tasks at pricise intervals
The delay os call simply halts a task for a period of time.
