Using function tick() the script is performed for each tick.
Not necessarily.
There is a chain...
BROKER <--> PLUGIN <--> ZORRO <--> tick()
Without SET_WHND:
* Broker says there is a tick.
* Plugin retains tick info or does nothing.
* (pause indefinitely)
* Broker says there is a tick.
* Plugin retains tick info or does nothing.
* (pause indefinitely)
* Zorro's timer says that it is time to check for a new tick on all Assets.
* Zorro gets the tick.
* Zorro invokes tick().
With SET_WHND:
* Broker says there is a tick.
* Plugin tells Zorro there is a tick.
* Zorro gets the tick.
* Zorro invokes tick().