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--- In UTTARA@yahoogroups.com, "lc_girish" <lc_girish@...> wrote:

>

> Hi Uttarait's

>

[..]

>

> * explain in detail where exactly volatile variables are used

>

The common understanding is that volatile tells the compiler it must not do certain optimizations. It means that the compiler must not optimize access to any variable that is declared volatile, even if the compiler knows that its value has not been changed between the last write access and the current read access.

Example:

    int i=0;
    
    ...             // i remain unchanged
    
    if (i==0)       // compiler knows i is 0 here
    {
    	... 
    }

Compiler knows that i must be 0 because there was no write access since it was initialized and it was not passed to any function that might have modified it. Hence a good compiler would optimize away the actual access to the memory location that represents variable i. Exactly this optimization is disabled for a volatile variable.

Additionally, for a note on volatile qualifier use in function parameters, please see the section 2.2.2.2 in http://oocities.com/vijoeyz/articles/c/pna/

Best,

Vijay Zanvar

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