On Oct 21, 2009, at 1:39 PM, Siddu wrote:
On Wed, Oct 21, 2009 at 8:32 AM, Rick Brown <rick.brown.3@xxxxxxxxx>
wrote:
Hi,
Firstly, I'm trying to understand what exactly characterizes a
procesor or an operating system as 32bit / 64 bit. I've read that it
means the "native word size" of a machine. But what exactly is that?
Register size? Address bus size? Anything else?
When they say its 32/64 bit machine its the capability of the system
or processor to process so many bits at once !
I had an understanding of this being how many bits you have to address
your RAM.
Secondly, I'm trying to understand what exactly does a sizeof(int)
depend on when we say it is "platform specific". Is it dependent of
compiler being 32bit / 64 bit? Or the OS being 32bit / 64 bit? Or the
processor being 32 / 64 bit?
its dependent on processor being 32/64 bit
Just did a comparison test but it tells me otherwise. But I'm not sure
if the test case if correct, can someone improve it?
On a 64bit CentOS:
[root@yyan ~]# more test.c
#include <stdio.h>
int main ()
{
printf ("%d\n", sizeof(int));
return 0;
}
[root@yyan ~]# gcc test.c
[root@yyan ~]# ./a.out
4
[root@yyan ~]# uname -a
Linux yyan.pmlab.com 2.6.18-128.el5 #1 SMP Wed Jan 21 10:41:14 EST
2009 x86_64 x86_64 x86_64 GNU/Linux
[root@yyan ~]#
On my Leopard: (Hopefully it's a 32bit OS as it shows)
simonmac:coding yansimon$ cat test.c
#include <stdio.h>
int main ()
{
printf ("%d\n", sizeof(int));
return 0;
}
simonmac:coding yansimon$ gcc test.c
simonmac:coding yansimon$ ./a.out
4
simonmac:coding yansimon$ uname -a
Darwin simonmac.local 9.8.0 Darwin Kernel Version 9.8.0: Wed Jul 15
16:55:01 PDT 2009; root:xnu-1228.15.4~1/RELEASE_I386 i386
simonmac:coding yansimon$
Lastly, How are "sizes" of compiler / OS / processor inter related?
Here is my understanding. A 32 bit processor can only be running a 32
bit OS.
No ... 32 bit OS can run anything <= 32 bit
A 64 bit processor may run a 32 or a 64 bit OS.
yes thats right !
A 32 bit
compiler genrates code only to be run on a 32 bit OS; ditto for 64
bit.
Not sure about this let others have their say !
Is this right?
Please correct me if i am wrong !
TIA,
Rick
--
To unsubscribe from this list: send an email with
"unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx
Please read the FAQ at http://kernelnewbies.org/FAQ
--
Regards,
~Sid~
I have never met a man so ignorant that i couldn't learn something
from him
--
益牙
http://www.google.com/profiles/simonyanix
--
To unsubscribe from this list: send the line "unsubscribe linux-newbie" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.linux-learn.org/faqs
