How do you find out if a machine is 32 bit or 64 bit?

[codergem]

One common answer is that all compilers keep the size of integer the
same as the size of the register on a particular architecture. Thus, to
know whether the machine is 32 bit or 64 bit, just see the size of
integer on it.

Is it Correct??
Or there any other way of finding it out?
Do I need to mention that through a C++ program..??

[Ian Collins]

co******@gmail. com wrote:

One common answer is that all compilers keep the size of integer the
same as the size of the register on a particular architecture. Thus, to
know whether the machine is 32 bit or 64 bit, just see the size of
integer on it.

Is it Correct??
No.
Or there any other way of finding it out?

sizeof(void*) is a better bet, but why would a running program care?

--
Ian Collins.

[codergem]

But the sizes of an int and void* is same.
as far as i know.
And yes these sizes tell about the compiler is 16bit or 32 bit.
and the ques is to find out of a machine.
So are both the things same?

Ian Collins wrote:

co******@gmail. com wrote:

One common answer is that all compilers keep the size of integer the
same as the size of the register on a particular architecture. Thus, to
know whether the machine is 32 bit or 64 bit, just see the size of
integer on it.

Is it Correct??

No.

Or there any other way of finding it out?

sizeof(void*) is a better bet, but why would a running program care?

--
Ian Collins.

[Alex Buell]

On 6 Jun 2006 17:01:11 -0700, I waved a wand and this message magically
appeared from co******@gmail. com:

One common answer is that all compilers keep the size of integer the
same as the size of the register on a particular architecture. Thus,
to know whether the machine is 32 bit or 64 bit, just see the size of
integer on it.

Is it Correct??

No. Something like this will do the trick for integers, as below. You
will need to include <limits> in your code.

const int bits = std::numeric_li mits<int>::digi ts;

Then if the type is really 32 bits, the variable bits will contain the
value 32. It's that simple.
--
http://www.munted.org.uk

Take a nap, it saves lives.

[Ian Collins]

co******@gmail. com wrote:

Please don't top post! fixed.

Ian Collins wrote:

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

One common answer is that all compilers keep the size of integer the
same as the size of the register on a particular architecture. Thus, to
know whether the machine is 32 bit or 64 bit, just see the size of
integer on it.

Is it Correct??

No.

Or there any other way of finding it out?

sizeof(void *) is a better bet, but why would a running program care?

But the sizes of an int and void* is same.
as far as i know.
And yes these sizes tell about the compiler is 16bit or 32 bit.
and the ques is to find out of a machine.
So are both the things same?

They most likely are not the same on a 64 bit system, try this example:

#include <iostream>

int
main()
{
std::cout << sizeof(int) << std::endl;
std::cout << sizeof(long) << std::endl;
std::cout << sizeof(void*) << std::endl;
}

I still don't know what you are trying to achieve, if a program is
compiled on a 32 system, or 32 bit on a 64 bit system, it will run as 32
bit no matter what the machine architecture is.

There may be a target specific means to determine the machine size, but
there isn't a standard C++ one.

--
Ian Collins.

[John Carson]

<co******@gmail .com> wrote in message
news:11******** **************@ g10g2000cwb.goo glegroups.com

But the sizes of an int and void* is same.
as far as i know.

You know wrong. On 64 bit Windows systems, an int is 32 bits and a pointer
is 64 bits.

If you want to write a program for a 64 bit system, you will need a new
compiler or at least you need to set a switch on the compiler. As Ian
suggests, if you compile a 32 bit program and run it on a 64 bit system,
then it works via the 64 bit system emulating a 32 bit system. Thus it is
always your compiler that determines whether you need to program for a 32
bit or 64 bit environment.

If you want to use a common code base for both 32 bit and 64 bit programs,
you can test in your code for the compiler or compiler switch. Mostly, you
should just avoid making any assumptions about size in your coding. Size
should only become an issue with vendor specific extensions to the Standard.

--
John Carson

[yoleung]

I am not sure I am asking the correct question
When we say 32/64 bit, are we talking the addressing mode or the
instruction size, yes, most processor nowadays insycn these two values,
but not necessary always,

For example, instruction size could be 32 bit while addressing is 64
bit, just one memory slot contains two instruction, possible?
co******@gmail. com wrote:

One common answer is that all compilers keep the size of integer the
same as the size of the register on a particular architecture. Thus, to
know whether the machine is 32 bit or 64 bit, just see the size of
integer on it.

Is it Correct??
Or there any other way of finding it out?
Do I need to mention that through a C++ program..??

[Ian Collins]

yo*****@gmail.c om wrote:

I am not sure I am asking the correct question
When we say 32/64 bit, are we talking the addressing mode or the
instruction size, yes, most processor nowadays insycn these two values,
but not necessary always,

For example, instruction size could be 32 bit while addressing is 64
bit, just one memory slot contains two instruction, possible?

Please don't top post!

<OT> The general loose definition of a processor's bit size is its
register and ALU - the CPU core - sizes.

A processor can have a 64 core, but be restricted to a smaller address
range or external data bus size. It is still a 64 bit processor.

The instruction size on most modern CPUs is variable.</OT>

--
Ian Collins.

[Patrick]

Ian Collins wrote:

yo*****@gmail.c om wrote:

I am not sure I am asking the correct question
When we say 32/64 bit, are we talking the addressing mode or the
instruction size, yes, most processor nowadays insycn these two values,
but not necessary always,

For example, instruction size could be 32 bit while addressing is 64
bit, just one memory slot contains two instruction, possible?

Please don't top post!

<OT> The general loose definition of a processor's bit size is its
register and ALU - the CPU core - sizes.

A processor can have a 64 core, but be restricted to a smaller address
range or external data bus size. It is still a 64 bit processor.

The instruction size on most modern CPUs is variable.</OT>

--
Ian Collins.

So do you mean the size of the register?

[Noah Roberts]

co******@gmail. com wrote:

One common answer is that all compilers keep the size of integer the
same as the size of the register on a particular architecture. Thus, to
know whether the machine is 32 bit or 64 bit, just see the size of
integer on it.

Is it Correct??
Or there any other way of finding it out?
Do I need to mention that through a C++ program..??

sizeof int is 4 on amd64.

long might be a better choice. Is it not specified in the standard as
the word size of the architecture? Oh well, not near by...you'll have
to check.

Or as someone said, void* is supposed to be big enough to hold any
pointer, no? Don't know if it has to be word size by standard or not
though...but it likely is.