Floats on 64 bit machines

[ulvr]

Just a quick question -- are floats on 64 bit machines (Windows/Linux)
still going to be 4 bytes, or will they be 8 bytes? Is there any
guarentee that a float is four bytes?

John

[Victor Bazarov]

ul**@rogers.com wrote:

Just a quick question -- are floats on 64 bit machines (Windows/Linux)
still going to be 4 bytes, or will they be 8 bytes?

I've only seen 4-byte floats so far. The Standard does not require the
upper limit, though, only the lower limit.

Is there any
guarentee that a float is four bytes?

No.

V
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[Pete Becker]

On 2008-06-12 16:20:35 +0200, ul**@rogers.com said:

Just a quick question -- are floats on 64 bit machines (Windows/Linux)
still going to be 4 bytes, or will they be 8 bytes? Is there any
guarentee that a float is four bytes?

The C++ Standard doesn't say much about sizes of floats and doubles.
Many systems implement IEEE-754, which provides a 32-bit single format
and a 64-bit double format. Those are typically mapped to float and
double, respectively.

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Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The
Standard C++ Library Extensions: a Tutorial and Reference
(www.petebecker.com/tr1book)

[James Kanze]

On Jun 12, 4:20 pm, [e-mail] wrote:

Just a quick question -- are floats on 64 bit machines
(Windows/Linux) still going to be 4 bytes, or will they be 8
bytes? Is there any guarentee that a float is four bytes?

No, there never has been. There's probably a minimum size (in
bits), because the standard does make some guarantees concerning
range and precision, but it's difficult to establish, since the
standard allows different bases. And there's definitely no
maximum size.

If you limit yourself to machines with IEEE floating point, then
you can pretty much count on a float being 32 bits---for most
machines, this will mean a size of 4 (but from what I've heard,
on some DSP, it will be a size of 1).

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