decimal fraction to binary conversion

hend

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Dec 2, 2011, 6:02:09 AM12/2/11

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Hello everybody;

i'm in need to a program code which can convert negative fractions into binary form ( any form ) ..
dec2bin command is not helpful in this case !

ade77

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Dec 2, 2011, 9:49:08 AM12/2/11

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"hend " <eng.h...@yahoo.com> wrote in message <jbab7h$47b$1...@newscl01ah.mathworks.com>...

> Hello everybody;
>
> i'm in need to a program code which can convert negative fractions into binary form ( any form ) ..
> dec2bin command is not helpful in this case !

You can take advantage of the fact that Java is installed along with ur MATLAB. if u know basic Java, then u can do work around it.

For example to convert -5 to binary.... at the command prompt, type:
java.lang.Integer.toBinaryString(-5)

if ur Java is good enough , u will be able to find a way to handle the negative fraction and the number of bits been displayed.

Optionally, write a MATLAB program to handle what u want to do, and post it to the file exchange...... lol

Jonathan

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Dec 2, 2011, 9:51:08 AM12/2/11

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"hend " <eng.h...@yahoo.com> wrote in message <jbab7h$47b$1...@newscl01ah.mathworks.com>...

> Hello everybody;
>
> i'm in need to a program code which can convert negative fractions into binary form ( any form ) ..
> dec2bin command is not helpful in this case !

There are several problems here. You will have to utilize a scheme such as Two's complement in order to represent both positive and negative numbers in binary form.

You will need to add a sign bit before the binary number representing the number. So if you want to represent +5, 5 would typically be 101, but add a sign bit and it becomes 0101. Now to represent a negative number, your sign bit will be 1 and the following numbers will be the two's complement of 5 and you end up with 1011.

You can read more here:
http://en.wikipedia.org/wiki/Two's_complement

Also, dec2bin doesn't handle fractions like you think, it returns the binary representation of only the integer portion of your input.

Roger Stafford

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Dec 2, 2011, 4:25:09 PM12/2/11

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"hend " <eng.h...@yahoo.com> wrote in message <jbab7h$47b$1...@newscl01ah.mathworks.com>...

> i'm in need to a program code which can convert negative fractions into binary form ( any form ) ..
> dec2bin command is not helpful in this case !

- - - - - - - - -
You can use 'dec2bin' if you help it out a bit. As an example, suppose you want to display 16 fractional binary digits on the number -1/(4*pi).

d = 16;
x = -1/(4*pi);

b = sign(x);
t = round(2^d*abs(x));
[~,e] = log2(t);
s = dec2bin(t,max(d,e));
s = [s(1:end-d),'.',s(end-d+1:end)];
if b<0, s = ['-',s]; end

The string s is the result. This code may not be quite the format you want but if not perhaps you can modify it appropriately.

Roger Stafford

hend

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Dec 3, 2011, 12:44:08 AM12/3/11

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Thanks all ..

Shyamsunder

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Dec 20, 2011, 2:03:08 AM12/20/11

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"Roger Stafford" wrote in message <jbbfnl$8v6$1...@newscl01ah.mathworks.com>...

Hi Roger,

How will you convert the negative fractional binary number back to the decimal number?

With regards,
Shyamsunder