Serial Event Structures

[SercoSteveB]

The user runs the following VI and then performs a single left mouse click and release on the control named Boolean.  What is the resulting value of Numeric Value Out?

NOTE:  Boolean Control is configured for Switch Until Released mechanical action

a) 0

b) 1

c) 2

d) Undefined (the VI does not stop)

[LordNobady]

C.

The value Change gives 2 events for a single click and release. one for the click ( change to 1 ) and one for the release ( change to 0 )

And if I am not mistaken the event structure quees the events so even events that where triggered before it was waiting for it, ( not that where triggerd before initalization ) will be executed.

[adiveppa]

Ans is C

[crossrulz]

C

Each event structure has its own queue and each event structure that is registered to an event will see the event.  Events are a lot like notifiers in this regard.

[mini09]

Accepted C as well....

[RAMESHB]

Ans is C.

[taper]

C, but not for the reason you may think.  Both event structures are triggered by the initial click.  The above vi will finish and display 2 even if you never release the button.  If you had these structures in while loops(like you should), they would each trigger twice on a click and release.  Doesn't matter if the 2nd event structure isn't executed until after the click and release is finished.

[crossrulz]

taper wrote:

                       

C, but not for the reason you may think.  Both event structures are triggered by the initial click.  The above vi will finish and display 2 even if you never release the button.  If you had these structures in while loops(like you should), they would each trigger twice on a click and release.  Doesn't matter if the 2nd event structure isn't executed until after the click and release is finished.

                   

That's what you call over analysing the question.  The point here is that each event structure will trigger on the first value change of the button.  The second event structure will have the event queued, but won't be able to run until the first event structure is complete.

BTW, I have plenty of VIs running around that have event structures not in loops.  They are dialog VIs and only look for a OK or Cancel.

[SercoSteveB]

So taper what are we saying here?  That it doesn't matter what point in the dataflow we have reached, all event structures in a VI (with a particular event registered) will queue that event, when it occurs, and execute it when the dataflow reaches them?

That is my thing to learn today.  Nice one.

[MrStevenUND]

C

[SercoSteveB]

Answer: C.  Nice one LordNobady, adiveppa, crossrulz, gnshmrthy, RAMESHB, taper & MrStevenUND.

Just when I think I have got Event Structures down, a snippet of information comes along that aligns things up just that little bit better, thanks taper.