how to detect CPU architecture..

[rrs.matrix]

hi
i have to detect the type of CPU.
whether it is 32-bit or 64-bit..
how can this be done..

can anyone please help me..

thanks.

[jaysome]

On 31 Aug 2006 23:14:23 -0700, rr********@gmai l.com wrote:

>hi
i have to detect the type of CPU.
whether it is 32-bit or 64-bit..
how can this be done..

can anyone please help me..

thanks.

Standard C does not provide any way to detect whether the type of CPU
is 32-bit or 64-bit or even 8-bit or 16-bit or 128-bit. Since this
newsgroup is about Standard C, no one here can really help you.

--
jay

[Richard Bos]

rr********@gmai l.com wrote:

i have to detect the type of CPU.
whether it is 32-bit or 64-bit..
how can this be done..

It can't. The CPU is 8-bit.

Richard






(Well, it could be. I still have computers like that. And define "the
type". And explain why you want to know. You probably _think_ you need
to, but you're equally probably mistaken.)

[dkrot]

Try to use ULONG_MAX in gcc macro if you use Unix.
or sizeof(long): 4 for 32bit, 8 for 64bit arch.

[Walter Roberson]

In article <7a************ *************** *****@4ax.com>,
jaysome <ja*****@spamco p.netwrote:

>On 31 Aug 2006 23:14:23 -0700, rr********@gmai l.com wrote:

>>i have to detect the type of CPU.
whether it is 32-bit or 64-bit..
how can this be done..

>Standard C does not provide any way to detect whether the type of CPU
is 32-bit or 64-bit or even 8-bit or 16-bit or 128-bit. Since this
newsgroup is about Standard C, no one here can really help you.

Furthermore, Standard C does not provide any what to determine what any
particular person -means- by a CPU being 32 bit or 64 bit or something
else. Bits in int? Bits in long? Bits in long long? Bits in a pointer?
Maximum theoretical addressible memory? Bits in the data bus between
the CPU and memory? Maximum number of bits in a result produced by an
operation? (that's a trick question -- integer multiple and divide
instructions are often exceptions to the rest of the architecture.)

Then there are systems like all of the SGI MIPS-based computers
produced in the last decade, all of which have CPUs which can
switch between 32 bit pointers and 64 bit pointers (per process),
any particular test run would not tell you what the CPU is capable
of, only how that particular test program was set up to run.
--
Prototypes are supertypes of their clones. -- maplesoft

[Frederick Gotham]

posted:

hi
i have to detect the type of CPU.
whether it is 32-bit or 64-bit..
how can this be done..

I suppose the closest thing might be something like:

#include <limits.h>

#if UINT_MAX == 4294967295U
/* We have 32-Bit */
#elsif UINT_MAX == 184467440737095 51615U
/* We have 64-Bit */
#else
/* Neither */
#endif

--

Frederick Gotham

[jacob navia]

Frederick Gotham wrote:

posted:

>>hi
i have to detect the type of CPU.
whether it is 32-bit or 64-bit..
how can this be done..

I suppose the closest thing might be something like:

#include <limits.h>

#if UINT_MAX == 4294967295U
/* We have 32-Bit */
#elsif UINT_MAX == 184467440737095 51615U
/* We have 64-Bit */
#else
/* Neither */
#endif

No. This would "detect" a 32 bit system in a 64 bit
unix. Use "long" for that. In 64 bit Unix, you have
(in some implementations , specifically gcc)
long 64 bits
int 32 bits

64 bit windows has
long 32 bits
int 32 bits

jacob

[Walter Roberson]

In article <FI************ *******@news.in digo.ie>,
Frederick Gotham <fg*******@SPAM .comwrote:
[someone not named by Frederick posted]

>i have to detect the type of CPU.
whether it is 32-bit or 64-bit..

>I suppose the closest thing might be something like:

>#include <limits.h>

>#if UINT_MAX == 4294967295U
/* We have 32-Bit */
#elsif UINT_MAX == 184467440737095 51615U
/* We have 64-Bit */
#else
/* Neither */
#endif

SGI IRIX in -64 mode would have UINT_MAX as 4294967295U .

Perhaps you meant to use ULONG_MAX instead of UINT_MAX ?
--
Is there any thing whereof it may be said, See, this is new? It hath
been already of old time, which was before us. -- Ecclesiastes

[Frederick Gotham]

jacob navia posted:

No. This would "detect" a 32 bit system in a 64 bit
unix.

Yes, I realise that. It was a merely fully-portable attempt to detect CPU
bitness.

--

Frederick Gotham

[Keith Thompson]

"dkrot" <j.*****@ramble r.ruwrites:

Try to use ULONG_MAX in gcc macro if you use Unix.
or sizeof(long): 4 for 32bit, 8 for 64bit arch.

Please quote enough context so we can tell what you're talking about
even if we haven't seen the parent article.

ULONG_MAX (which is standard C, not specific to either gcc or Unix)
only tells you what the compiler writer has chosen as the maximum
value of type unsigned long. It tells you nothing about the
underlying CPU architecture. The compiler writer's choices for the
attributes of the predefined types are typically guided by the CPU
architecture, but they're not mandated by it.

It's not even clear what "32-bit architecture" or "64-bit
architecture" actually means. It might have some accepted meaning for
particular sets of architectures (e.g., the x86 family), but that
won't necessarily apply to other architectures (PowerPC, SPARC,
AS/400, DS9K, etc.).

And even if you can rigorously define the terms, there's not likely to
be any way to distinguish between them in portable C.

The entire question is largely meaningless and off-topic.

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <* <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.