Floating point number to binary

[Gaurav Verma]

Hi,

I want to convert a floating point number (or a decimal number say
123.456) into binary notation using a C program. Can somebody help me
out with it?

Thanks
Gaurav
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[Kenneth Brody]

Gaurav Verma wrote:

Hi,

I want to convert a floating point number (or a decimal number say
123.456) into binary notation using a C program. Can somebody help me
out with it?

float MyNum = 123.456;

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[Walter]

"Gaurav Verma" <ve**********@g mail.com> wrote in message
news:cl******** ********@pletho ra.net...

I want to convert a floating point number (or a decimal number say
123.456) into binary notation using a C program. Can somebody help me
out with it?

Here's a simple program that does it for Digital Mars C:

#include <stdio.h>

int main()
{
double d = 123.456;
printf("%032b %032b\n", ((int*)&d)[0], ((int*)&d)[1]);
return 0;
}

which prints:

000110101001111 110111110011101 11 010000000101111 011011101001011 11

Of course, it relies on some non-standard behavior, like the %b format for
binary, it assumes that sizeof(double)= =2*sizeof(int)= =64 bits, and there
are endianness issues. But this should help in seeing how it might be done.

-Walter
www.digitalmars.com free C/C++/D compilers
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[jmh]

Gaurav Verma wrote:

Hi,

I want to convert a floating point number (or a decimal number say
123.456) into binary notation using a C program. Can somebody help me
out with it?

Thanks
Gaurav

One approach wuold be to split the number into it's integer
and it's fractional parts, use the division-remainder method
to convert the integer part to a string representatin of the
binary value (i.e., case all the 1s and 0s as char and then
contatinate them) they apply the mulitple-remainder (is that
what it's called?) method to the frational part and do the
same casts, then concatinate the two parts together.
jmh
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[pete]

Nicolas Pavlidis wrote:

unsigned char comp_mask = 0x1 << ((sizeof(char) * 8) -1);
char* bin_rep = malloc(sizeof(c har) * sizeof(char) * 8 + 1);

Those statements won't do what you want, unless CHAR_BIT equals 8.
sizeof(char) always equals 1, so it's a little strange to use
sizeof(char) as a multiplicand in an expression.
If 8 is replaced by CHAR_BIT, then the 0x1 expression, would
also have to be replaced by one with an unsigned type, like 1u.

--
pete

[Nicolas Pavlidis]

pete <pf*****@mindsp ring.com> writes:

Nicolas Pavlidis wrote:

unsigned char comp_mask = 0x1 << ((sizeof(char) * 8) -1);
char* bin_rep = malloc(sizeof(c har) * sizeof(char) * 8 + 1);

Those statements won't do what you want, unless CHAR_BIT equals 8.
sizeof(char) always equals 1, so it's a little strange to use
sizeof(char) as a multiplicand in an expression.
If 8 is replaced by CHAR_BIT, then the 0x1 expression, would
also have to be replaced by one with an unsigned type, like 1u.

It was code I wrote for some assignement on a university course.
At that time I didn't know that sizeof(char) == 1, on all platforms,
CHAR_BIT would be better here.

But I had no problems on 32bit Linux.

Kind regards,
Nicolas
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[Mark McIntyre]

On 16 Sep 2004 06:32:19 GMT, in comp.lang.c , ve**********@gm ail.com
(Gaurav Verma) wrote:

Hi,

I want to convert a floating point number (or a decimal number say
123.456) into binary notation using a C program. Can somebody help me
out with it?

It will almost certainly be pointed out to you by many people that all
numbers in C are already in binary format (unless you're one of the rare
people with a nonbinary computer).

I expect you mean you want to print out the bitpattern of a floating point
value. Thats not really a C question, its a question about how to translate
the floating point format for your hardware.

Once you know, that, simply iterate over the bits of the number, printing a
1 for each set bit and a 0 for each unset bit.
--
Mark McIntyre
CLC FAQ <http://www.eskimo.com/~scs/C-faq/top.html>
CLC readme: <http://www.ungerhu.com/jxh/clc.welcome.txt >
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