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doubt on volatile data type
Joined: 28 Dec 2004
Posts: 3
doubt on volatile data type
Hi all,
what is volatile data type mean???
why?? when it used??
can a varible be declared as both volatile & const
type?
(const volatile int i;)
Rgds
Madhuar
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Joined: 02 Jan 2005
Posts: 9
doubt on volatile data type
--- Madhukar mythri <madhukar_linux@...>
wrote:
>
> Hi all,
> what is volatile data type mean???
> why?? when it used??
>
> can a varible be declared as both volatile & const
> type?
> (const volatile int i;)
>
>
> Rgds
> Madhuar
Hi Madhur,
A volatile data type is usually a type which is shared
between two threads of a process. We need to specify
them volatile to the compiler so that whenever the
compiler needs to access it, it accesses it from the
original location of the memory and not from the
cache, as it might be changed by the other thread.
With Regards
Manik
>
>
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Joined: 29 Dec 2004
Posts: 31
doubt on volatile data type
From: Madhukar mythri [mailto:madhukar_linux@...]
>Hi all,
> what is volatile data type mean???
It tells the compiler that it cannot assume that the value of the
variable will stay the same between two consecutive reads. For example
in the following code, the compiler may assume j will not change:
int j
for(j=0; j<10; j++){
/* code that does NOT modify j */
}
>why?? when it used??
When something external to the code under consideration may modify the
variable. Examples include another thread in the same program, or the
variable may be mapped to external I/O.
>can a varible be declared as both volatile & const
>type?
>(const volatile int i;)
Yes. If (for example) it is a `read only`, for example I/O Mapped serial
comms in. There would be no point in allowing the programmer to write to
this point.
--
PJH
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lacking zero, they had no way to indicate successful termination of
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Joined: 25 Jul 2003
Posts: 48
doubt on volatile data type
Reply embedded...
> -----Original Message-----
> From: Madhukar mythri [mailto:madhukar_linux@...]
> Sent: Wednesday, January 05, 2005 2:04 AM
> To: Programmers-Town@yahoogroups.com
> Subject: (PT) doubt on volatile data type
>
>
>
> Hi all,
> what is volatile data type mean???
The object can be modified outside the control and knowledge of your code,
or unknown side effects.
> why??
Because it is not "stable".
> when it used??
When you need to access object with volatile properties. It tells the
compiler not to assume that the value stays between read.
> can a varible be declared as both volatile & const
> type?
> (const volatile int i;)
Yes. They are not oxymoron.
`const` means you will not change it within your code, i.e. read-only.
`volatile` means it is changed by means outside the control of your program,
so compiler should always read the current value of the object instead of
assume it never changed.
HTH
Shyan
Joined: 28 Dec 2004
Posts: 3
doubt on volatile data type
Hi ,
Thanks for reply...
Rgds
Madhukar
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