Does "float" always occupy 32 bits

[chandanlinster]

As far as I know floating point variables, that are declared as float
follow IEEE format representation (which is 32-bit in size). But
chapter1-page no 9 of the book "The C programming language" states that
"THE RANGE OF BOTH int AND float DEPENDS ON THE MACHINE YOU ARE
USING".
Does this mean "float" variables have different sizes on different
machines?

[Skarmander]

chandanlinster wrote:

As far as I know floating point variables, that are declared as float
follow IEEE format representation (which is 32-bit in size). But
chapter1-page no 9 of the book "The C programming language" states that
"THE RANGE OF BOTH int AND float DEPENDS ON THE MACHINE YOU ARE
USING".
Does this mean "float" variables have different sizes on different
machines?

Yes.

Although the IEEE single-precision type is the most common implementation of
float, this is not required. The standard only requires a minimum range and
minimum precision. Implementations can optionally signal that they implement
IEC 60559, a revision of IEEE 754.

In practice, most programs do not depend on the particular size of a float;
the ones that assume are usually those who also assume an int is 32 bits, so
floats and ints can be stored interchangeably . Needless to say, these are
not portable assumptions, and rarely appropriate, let alone necessary.

S.

[Philip Potter]

"chandanlinster " <ch************ @gmail.comwrote in message
news:11******** **************@ e3g2000cwe.goog legroups.com...

As far as I know floating point variables, that are declared as float
follow IEEE format representation (which is 32-bit in size).

This is not guaranteed.

But
chapter1-page no 9 of the book "The C programming language" states that
"THE RANGE OF BOTH int AND float DEPENDS ON THE MACHINE YOU ARE
USING".
Does this mean "float" variables have different sizes on different
machines?

Yes.

Philip

[rramesh1]

Hi Guys.

I have a AMD-64 turion running debian Linux with gcc & here is what I
got..

char:1
short:2
long:8
float:4
double:8
long double:16

Here are my compiler options..

Using built-in specs.
Target: x86_64-linux-gnu
Configured with: ../src/configure -v
--enable-languages=c,c++ ,java,fortran,o bjc,obj-c++,ada,treelan g
--prefix=/usr --enable-shared --with-system-zlib --libexecdir=/usr/lib
--without-included-gettext --enable-threads=posix --enable-nls
--program-suffix=-4.1 --enable-__cxa_atexit --enable-clocale=gnu
--enable-libstdcxx-debug --enable-java-awt=gtk --enable-gtk-cairo
--with-java-home=/usr/lib/jvm/java-1.4.2-gcj-4.1-1.4.2.0/jre
--enable-mpfr --enable-checking=releas e x86_64-linux-gnu
Thread model: posix
gcc version 4.1.2 20060613 (prerelease) (Debian 4.1.1-5)

Cheers
/R

Philip Potter wrote:

"chandanlinster " <ch************ @gmail.comwrote in message
news:11******** **************@ e3g2000cwe.goog legroups.com...

As far as I know floating point variables, that are declared as float
follow IEEE format representation (which is 32-bit in size).

This is not guaranteed.

But
chapter1-page no 9 of the book "The C programming language" states that
"THE RANGE OF BOTH int AND float DEPENDS ON THE MACHINE YOU ARE
USING".
Does this mean "float" variables have different sizes on different
machines?

Yes.

Philip

[chandanlinster]

Thanks everybody for providing the solutions.

[Keith Thompson]

"chandanlinster " <ch************ @gmail.comwrite s:

As far as I know floating point variables, that are declared as float
follow IEEE format representation (which is 32-bit in size). But
chapter1-page no 9 of the book "The C programming language" states that
"THE RANGE OF BOTH int AND float DEPENDS ON THE MACHINE YOU ARE
USING".
Does this mean "float" variables have different sizes on different
machines?

Potentially, yes.

I've never heard of a C implementation where float is not 32 bits
(i.e., where sizeof(float) * CHAR_BIT != 32), but such implementations
could easily exist.

In any case, there's no real reason or need to assume that float is 32
bits. The compiler knows how big a float is so you don't need to
worry about it.

--
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.

[Ben Pfaff]

Keith Thompson <ks***@mib.orgw rites:

"chandanlinster " <ch************ @gmail.comwrite s:

>As far as I know floating point variables, that are declared as float
follow IEEE format representation (which is 32-bit in size). But
chapter1-page no 9 of the book "The C programming language" states that
"THE RANGE OF BOTH int AND float DEPENDS ON THE MACHINE YOU ARE
USING".
Does this mean "float" variables have different sizes on different
machines?

Potentially, yes.

I've never heard of a C implementation where float is not 32 bits
(i.e., where sizeof(float) * CHAR_BIT != 32), but such implementations
could easily exist.

I don't think that float could be much smaller than 32 bits. By
my calculations, a floating point number represented in the
format that the Standard expects would need approximately 28 bits
to have the required range and precision.
--
"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it."
--Brian Kernighan

[Keith Thompson]

Ben Pfaff <bl*@cs.stanfor d.eduwrites:

Keith Thompson <ks***@mib.orgw rites:

>"chandanlinste r" <ch************ @gmail.comwrite s:

>>As far as I know floating point variables, that are declared as float
follow IEEE format representation (which is 32-bit in size). But
chapter1-page no 9 of the book "The C programming language" states that
"THE RANGE OF BOTH int AND float DEPENDS ON THE MACHINE YOU ARE
USING".
Does this mean "float" variables have different sizes on different
machines?

Potentially, yes.

I've never heard of a C implementation where float is not 32 bits
(i.e., where sizeof(float) * CHAR_BIT != 32), but such implementations
could easily exist.

I don't think that float could be much smaller than 32 bits. By
my calculations, a floating point number represented in the
format that the Standard expects would need approximately 28 bits
to have the required range and precision.

Sure, but float could easily be larger than 32 bits.

And, in fact, contrary to what I wrote above, I've worked on machines
where float is 64 bits (and double is 64 bits, and long double is 128
bits). These were Cray vector machines, where the native word size is
64 bits.

--
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.

[Ben Pfaff]

Keith Thompson <ks***@mib.orgw rites:

Ben Pfaff <bl*@cs.stanfor d.eduwrites:

>Keith Thompson <ks***@mib.orgw rites:

>>I've never heard of a C implementation where float is not 32 bits
(i.e., where sizeof(float) * CHAR_BIT != 32), but such implementations
could easily exist.

I don't think that float could be much smaller than 32 bits. By
my calculations, a floating point number represented in the
format that the Standard expects would need approximately 28 bits
to have the required range and precision.

Sure, but float could easily be larger than 32 bits.

Yes, I should have added that. I didn't mean to sound contradictory.

And, in fact, contrary to what I wrote above, I've worked on machines
where float is 64 bits (and double is 64 bits, and long double is 128
bits). These were Cray vector machines, where the native word size is
64 bits.

Right.
--
"I should killfile you where you stand, worthless human." --Kaz

[Dik T. Winter]

In article <ln************ @nuthaus.mib.or gKeith Thompson <ks***@mib.orgw rites:

"chandanlinster " <ch************ @gmail.comwrite s:

....

Does this mean "float" variables have different sizes on different
machines?

Potentially, yes.

I've never heard of a C implementation where float is not 32 bits
(i.e., where sizeof(float) * CHAR_BIT != 32), but such implementations
could easily exist.

I have used them. sizeof(float) == 8.
--
dik t. winter, cwi, kruislaan 413, 1098 sj amsterdam, nederland, [phone]
home: bovenover 215, 1025 jn amsterdam, nederland; http://www.cwi.nl/~dik/