Static used on global variable declaration

I have inherited a CVI project that contains a single .C file and a couple of .UIR files with their associated .H files.
Many of the global variables have STATIC in their declaration - I believe this is due to the fact the original developer originally had them inside various functions and at some point changed strategy to make them global, leaving the STATIC keyword in place when copy/pasting.
As I understand it the ONLY implication of STATIC on a global variable would be to keep its visibility only to the .C file in which it is declared. In this instance that is moot since there is only one .C file in the project.
Is there anything about LabWindows/CVI which I might not be aware of that makes this use of STATIC cause something different than if STATIC were not used?
Thanks for any input you might have since I'm new to CVI

Roberto and menchar said it well:
"static variables are declared at compile time and survive when their block of code terminates. If declared at function level, their value survives from one call of the function to another, so that they can be used over time to store permanent values locale to the function. If declared at module level, they are common to all functions in the module and are allocated outside the stack so that their values are not lost during program life. In every case they can be accessed and modified in values by functions in the program. If arrays, they cannot be dinamically changed in size."
"The static keyword can be used with a function name also, meaning the function name isn't exported to the linker, and the function is in scope only to code within the module."

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5thGen wrote:
I have created a project that consists of several VIs. Only the main VI has a front panel and the others perform functions. The function VIs are dependent on controls on the main VI's front panel. I have several ways of passing the value of the controls.
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What are the advantages/disadvantages of these options?
-Stephen
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>
Sachidanand B wrote:
> Hi All,
>
> I need to validate a custom infotype field, where i need to check for execution times. I need to override the field value only during first time of the run(PAI logic) and there after user can choose a value of his choice.
> I was looking out for Global variable to check if its first run. Can you please tell me how do i create global variable in custom infotype? The top include specified in the program is not editable, being standard (MPH5ATOP).
>
> Thanks,
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Edited by: Uma Balasubramanya on Mar 20, 2009 1:11 PM

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I'm trying to learn how to use global variables, but can't quite get it right:
Im trying to use two buttons, named UpButton and DownButton to control one global variable, p1
A text field, named "Value" displays p1.
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In other browsers you may need to click "Show all content" or similar to any security warnings...
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Hi Katherine,
However, it seems to be treating p1 as two different variables.
Indeed, your code created two different variables in two different scopes (I guess it as to do with JavaScript closures, but do not ask me more, I am still a bit foggy about that idiosyncrasy ).
In JavaScript, a primitive parameter – this is the case here with p1, a Number value –, is passed by value. In other words, a copy of the value is made. Your code handles two copies of the value stored in p1.
This contrasts with an object parameter, which is passed by reference (address in memory), without copy. Your code would work if Numbers were passed by reference : the two Var (p1) would then point to the same address.
The intent behind your trial is a global variable.
1) Let us be as simple as possible :
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2) Now, suppose this is no longer the case : you want to access a variable from another symbol.
We create a new GraySquare symbol, instantiated both in the DownButton symbol (instance name DownSquare) and in the UpButton symbol (instance name DownSquare).
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p1 = 0;
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DownButton symbol : DownSquare.click event handler
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UpButton symbol : UpSquare.click event handler
sym.getComposition().getStage().buttonClick( 100);
From these other symbols, the sym.getComposition().getStage(). prefix is necessary to acces to our global variable (function).
The two examples are downloadable here : https://app.box.com/s/6vkyiqk7i8zwlw0j1wk1
Gil

Static used on global variable declaration

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