On Wed, Oct 21, 2009 at 12:02 AM, 益牙 <simonyanix@xxxxxxxxx> wrote:
I had an understanding of this being how many bits you have to address your RAM.
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 !
This is true, but it is also your instruction size. So the native machine code can be 64 bits on a 64bit processor.
- Show quoted text -
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?
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
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?
This is dependent on the compiler, or at least the compiler options. This is due to the machine code that the compiler generates.
ie. The difference between x86 machine code and ia64 machine code.
--
Please correct me if i am wrong !
TIA,
Rick
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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
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