Re: [algogeeks] Small Doubt

2011-07-28 Thread MANNU 
@Prem: Each program is provided with a pool of address, which consist
of heap, stack etc.
 My question is that if I write an address 0xff which is
not provided to that program then
 what will be the output?

On 7/28/11, Prem Krishna Chettri hprem...@gmail.com wrote:
 First of all this is a good Question as this is use regularly in Device
 Driver kind of Development Mode and hence there is no question of Not
 Possible.

 So how to Do it is Question. which is as follows :-

 Point your pointer to mem add that U want and Now this Mem Add is HEX guys
 (Not 4 or 5 or any base 10 val) , so put it as 0x(whatever U want).

 Do whatever  U want to do on that address using that pointer now.

 The Code above is correct but the implementation is wrong so...


 #includestdio.h
 int main()
 {
int *p = (int *)0xff;
   // *p = 4; /** Dude can U put hex val here .. Oh its already assigned
 to 0xff..  **/ Now print it coutpendl;
return 0;
 }

 Regards
  Prem

 On Thu, Jul 28, 2011 at 10:44 AM, Tyler Durden abhishek.khattr...@gmail.com
 wrote:

 @Ankita: So when is 4000 memory address is allotted?? I mean what use does
 int *p = 4000 serve here??

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Re: [algogeeks] Small Doubt

2011-07-28 Thread Prem Krishna Chettri 
Hey.. good To have your Question . Well lemme try to elaborate things here
as i cannot use WhiteBoard . So Srry guys... :(

Well partly you have answered your question and some part can even be
reflected in the above thread of virtual - physical mem mapping. using MMU..
So I wont go beyond MMU.

Here it goes.

Well if you write a prg.. when it bcme process, OS assign a  bunch of ID as
Address which it can use in sense. However, this address are not what is
real add.there is what MMU kicks in...

So if 0xff U think is assigned its not actually its is mapped with something
like this .. PID + 0x0ff = xyzxyx( Hell anything let the OS answer it). that
MMU issue.

So, the question here is wat the case if the house you want is not in your
area. Dude you are not a kind to cry infront of your parent to get one for
U..

Similarly, OS will not give you the access directly to physical Mem ( under
his control ) hence, the pointer allocation may fail.

Now here comes the compiler of whatever type say g++ which may silently say
dude that house you want is unavailable or may keep quiet... but complains
when you are in need to stay in that house , or rather when you try to put
something within it.

So, the direct answer to your question is definitely your design of
Compiler. but rather I would like to say, the pointer allocation fails to
prove your address allocation.

Does that makes sense. lemme know for more without whiteboard.. :)

Regards
 Prem




On Thu, Jul 28, 2011 at 1:26 PM, MANNU manishkr2...@gmail.com wrote:

 @Prem: Each program is provided with a pool of address, which consist
 of heap, stack etc.
 My question is that if I write an address 0xff which is
 not provided to that program then
 what will be the output?

 On 7/28/11, Prem Krishna Chettri hprem...@gmail.com wrote:
  First of all this is a good Question as this is use regularly in Device
  Driver kind of Development Mode and hence there is no question of Not
  Possible.
 
  So how to Do it is Question. which is as follows :-
 
  Point your pointer to mem add that U want and Now this Mem Add is HEX
 guys
  (Not 4 or 5 or any base 10 val) , so put it as 0x(whatever U want).
 
  Do whatever  U want to do on that address using that pointer now.
 
  The Code above is correct but the implementation is wrong so...
 
 
  #includestdio.h
  int main()
  {
 int *p = (int *)0xff;
// *p = 4; /** Dude can U put hex val here .. Oh its already
 assigned
  to 0xff..  **/ Now print it coutpendl;
 return 0;
  }
 
  Regards
   Prem
 
  On Thu, Jul 28, 2011 at 10:44 AM, Tyler Durden 
 abhishek.khattr...@gmail.com
  wrote:
 
  @Ankita: So when is 4000 memory address is allotted?? I mean what use
 does
  int *p = 4000 serve here??
 
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Re: [algogeeks] Small Doubt

2011-07-27 Thread Anika Jain 
no we cant..
coz when we do say int *p=4000;
its fine till now.. and if we do *p=10; it is segmentation fault..

On Wed, Jul 27, 2011 at 10:35 PM, rShetty rajeevr...@gmail.com wrote:

 Usually when I declare a variable it will be stored in memory location
 with some address .
 Such as  consider I declare int x=10 , it will stored in some address
 1003 (say).
 Now my question is can I control the address being assigned to a
 variable in C . Say, I want to store x in address in 4000 and not in
 1003 defined by the compiler .(Usually this can be done in assembly).
 Can I do that ? Correct me If i am wrong

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Re: [algogeeks] Small Doubt

2011-07-27 Thread Anika Jain 
segmentation fault comes when we try to modify or do illegal access to the
memory that has not been allocated to us..
the trial to make your variable be at some location of your wish can be done
only by int *p=4000; *p=10;  but it is illegal coz 4000 memory address is
not alloted yet for your program.

On Wed, Jul 27, 2011 at 11:26 PM, Puneet Gautam puneet.nsi...@gmail.comwrote:

 @Anika : pls elaborate the segmentatin part...!


 On 7/27/11, Anika Jain anika.jai...@gmail.com wrote:
  no we cant..
  coz when we do say int *p=4000;
  its fine till now.. and if we do *p=10; it is segmentation fault..
 
  On Wed, Jul 27, 2011 at 10:35 PM, rShetty rajeevr...@gmail.com wrote:
 
  Usually when I declare a variable it will be stored in memory location
  with some address .
  Such as  consider I declare int x=10 , it will stored in some address
  1003 (say).
  Now my question is can I control the address being assigned to a
  variable in C . Say, I want to store x in address in 4000 and not in
  1003 defined by the compiler .(Usually this can be done in assembly).
  Can I do that ? Correct me If i am wrong
 
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Re: [algogeeks] Small Doubt

2011-07-27 Thread rajeev bharshetty 
@anika : I just found out that it can be done as

int *p = (int *)0x0ff ;
*p=4;

then 4 gets stored in 0x0ff location .
Guys can it be done . Is it Legal ??

On Thu, Jul 28, 2011 at 9:11 AM, Anika Jain anika.jai...@gmail.com wrote:

 segmentation fault comes when we try to modify or do illegal access to the
 memory that has not been allocated to us..
 the trial to make your variable be at some location of your wish can be
 done only by int *p=4000; *p=10;  but it is illegal coz 4000 memory address
 is not alloted yet for your program.


 On Wed, Jul 27, 2011 at 11:26 PM, Puneet Gautam 
 puneet.nsi...@gmail.comwrote:

 @Anika : pls elaborate the segmentatin part...!


 On 7/27/11, Anika Jain anika.jai...@gmail.com wrote:
  no we cant..
  coz when we do say int *p=4000;
  its fine till now.. and if we do *p=10; it is segmentation fault..
 
  On Wed, Jul 27, 2011 at 10:35 PM, rShetty rajeevr...@gmail.com wrote:
 
  Usually when I declare a variable it will be stored in memory location
  with some address .
  Such as  consider I declare int x=10 , it will stored in some address
  1003 (say).
  Now my question is can I control the address being assigned to a
  variable in C . Say, I want to store x in address in 4000 and not in
  1003 defined by the compiler .(Usually this can be done in assembly).
  Can I do that ? Correct me If i am wrong
 
  --
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*Winners Don't do Different things , they do things Differently*

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Re: [algogeeks] Small Doubt

2011-07-27 Thread Vishal Thanki 
@ rajeev,

vishal@ubuntu:~/progs/c\ 09:25:38 AM $ cat alg.c
#includestdio.h
int main()
{
int *p = (int *)0xff;
*p = 4;
return 0;
}

vishal@ubuntu:~/progs/c\ 09:25:42 AM $ gcc alg.c
vishal@ubuntu:~/progs/c\ 09:25:45 AM $ ./a.out
Segmentation fault
vishal@ubuntu:~/progs/c\ 09:25:46 AM $


On Thu, Jul 28, 2011 at 9:13 AM, rajeev bharshetty rajeevr...@gmail.com wrote:
 @anika : I just found out that it can be done as
 int *p = (int *)0x0ff ;
 *p=4;
 then 4 gets stored in 0x0ff location .
 Guys can it be done . Is it Legal ??

 On Thu, Jul 28, 2011 at 9:11 AM, Anika Jain anika.jai...@gmail.com wrote:

 segmentation fault comes when we try to modify or do illegal access to the
 memory that has not been allocated to us..
 the trial to make your variable be at some location of your wish can be
 done only by int *p=4000; *p=10;  but it is illegal coz 4000 memory address
 is not alloted yet for your program.

 On Wed, Jul 27, 2011 at 11:26 PM, Puneet Gautam puneet.nsi...@gmail.com
 wrote:

 @Anika : pls elaborate the segmentatin part...!


 On 7/27/11, Anika Jain anika.jai...@gmail.com wrote:
  no we cant..
  coz when we do say int *p=4000;
  its fine till now.. and if we do *p=10; it is segmentation fault..
 
  On Wed, Jul 27, 2011 at 10:35 PM, rShetty rajeevr...@gmail.com wrote:
 
  Usually when I declare a variable it will be stored in memory location
  with some address .
  Such as  consider I declare int x=10 , it will stored in some address
  1003 (say).
  Now my question is can I control the address being assigned to a
  variable in C . Say, I want to store x in address in 4000 and not in
  1003 defined by the compiler .(Usually this can be done in assembly).
  Can I do that ? Correct me If i am wrong
 
  --
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 Regards
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 Winners Don't do Different things , they do things Differently

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Re: [algogeeks] Small Doubt

2011-07-27 Thread kavitha nk 
whether al these address refer to the physical address or logical address???

On 7/28/11, Vishal Thanki vishaltha...@gmail.com wrote:
 @ rajeev,

 vishal@ubuntu:~/progs/c\ 09:25:38 AM $ cat alg.c
 #includestdio.h
 int main()
 {
   int *p = (int *)0xff;
   *p = 4;
   return 0;
 }

 vishal@ubuntu:~/progs/c\ 09:25:42 AM $ gcc alg.c
 vishal@ubuntu:~/progs/c\ 09:25:45 AM $ ./a.out
 Segmentation fault
 vishal@ubuntu:~/progs/c\ 09:25:46 AM $


 On Thu, Jul 28, 2011 at 9:13 AM, rajeev bharshetty rajeevr...@gmail.com
 wrote:
 @anika : I just found out that it can be done as
 int *p = (int *)0x0ff ;
 *p=4;
 then 4 gets stored in 0x0ff location .
 Guys can it be done . Is it Legal ??

 On Thu, Jul 28, 2011 at 9:11 AM, Anika Jain anika.jai...@gmail.com
 wrote:

 segmentation fault comes when we try to modify or do illegal access to
 the
 memory that has not been allocated to us..
 the trial to make your variable be at some location of your wish can be
 done only by int *p=4000; *p=10;  but it is illegal coz 4000 memory
 address
 is not alloted yet for your program.

 On Wed, Jul 27, 2011 at 11:26 PM, Puneet Gautam puneet.nsi...@gmail.com
 wrote:

 @Anika : pls elaborate the segmentatin part...!


 On 7/27/11, Anika Jain anika.jai...@gmail.com wrote:
  no we cant..
  coz when we do say int *p=4000;
  its fine till now.. and if we do *p=10; it is segmentation fault..
 
  On Wed, Jul 27, 2011 at 10:35 PM, rShetty rajeevr...@gmail.com
  wrote:
 
  Usually when I declare a variable it will be stored in memory
  location
  with some address .
  Such as  consider I declare int x=10 , it will stored in some address
  1003 (say).
  Now my question is can I control the address being assigned to a
  variable in C . Say, I want to store x in address in 4000 and not in
  1003 defined by the compiler .(Usually this can be done in assembly).
  Can I do that ? Correct me If i am wrong
 
  --
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 Regards
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Re: [algogeeks] Small Doubt

2011-07-27 Thread Tyler Durden 
@Ankita: So when is 4000 memory address is allotted?? I mean what use does 
int *p = 4000 serve here??

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Re: [algogeeks] Small Doubt

2011-07-27 Thread Prem Krishna Chettri 
First of all this is a good Question as this is use regularly in Device
Driver kind of Development Mode and hence there is no question of Not
Possible.

So how to Do it is Question. which is as follows :-

Point your pointer to mem add that U want and Now this Mem Add is HEX guys
(Not 4 or 5 or any base 10 val) , so put it as 0x(whatever U want).

Do whatever  U want to do on that address using that pointer now.

The Code above is correct but the implementation is wrong so...


#includestdio.h
int main()
{
   int *p = (int *)0xff;
  // *p = 4; /** Dude can U put hex val here .. Oh its already assigned
to 0xff..  **/ Now print it coutpendl;
   return 0;
}

Regards
 Prem

On Thu, Jul 28, 2011 at 10:44 AM, Tyler Durden abhishek.khattr...@gmail.com
 wrote:

 @Ankita: So when is 4000 memory address is allotted?? I mean what use does
 int *p = 4000 serve here??

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