What would be the best way to convert Hex to bin?
I am using this code to convert a Dec to Hex:

char hexstring[10];
unsigned int number = 800;
sprintf(hexstring, "%x", number);

What would be the next step for me to take?  I have to do it from Dec
to Hex and then from Hex to Binary?  Any suggestions would be really
appreciated.  Thank you very much

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Josh Parker <jcp1217@mail.ecu.edu> wrote:
> What would be the best way to convert Hex to bin?
> I am using this code to convert a Dec to Hex:

> char hexstring[10];
> unsigned int number = 800;
> sprintf(hexstring, "%x", number);

> What would be the next step for me to take?  I have to do it from Dec
> to Hex and then from Hex to Binary?  Any suggestions would be really
> appreciated.  Thank you very much

First of all that's not decimal to hex but what you do there is create
a string representation of the number stored in memory (in whatever
respresentation the machine likes, but you can be rather sure that
it's binary;-). You should also be careful, ints could be longer than
9 chars on some machines, in which case you might past the end of the
array for the string!

To get a binary string representation you write your own function,
something like this (but take care, it's completely untested):

char bin_string[ CHAR_BIT * sizeof( unsigned int ) + 1 ];
char *p = bin_string;
unsigned int number = 800;
unsigned int cur = 1 << ( CHAR_BIT * sizeof( unsigned int ) - 1 );

while ( cur )
{
*p++ = ( number & cur ) ? '1' : '0';
cur >>= 1;
}
*p = '\0';

Things get a tiny bit more complicted when you don't want leading
zeros, but that shouldn't be too difficult to figure out...

Regards, Jens
--
\   Jens Thoms Toerring  ___  Jens.Toerring@physik.fu-berlin.de
\__________________________  http://www.toerring.de

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Jens.Toerring@physik.fu-berlin.de wrote:

> Josh Parker <jcp1217@mail.ecu.edu> wrote:
>=20 
>=20
>=20 
>=20
>=20 
>=20
>=20
> First of all that's not decimal to hex but what you do there is create
> a string representation of the number stored in memory (in whatever
> respresentation the machine likes, but you can be rather sure that
> it's binary;-). You should also be careful, ints could be longer than
> 9 chars on some machines, in which case you might past the end of the
> array for the string!
>=20
> To get a binary string representation you write your own function,
> something like this (but take care, it's completely untested):
>=20
> char bin_string[ CHAR_BIT * sizeof( unsigned int ) + 1 ];
> char *p =3D bin_string;
> unsigned int number =3D 800;
> unsigned int cur =3D 1 << ( CHAR_BIT * sizeof( unsigned int ) - 1 );
>=20
> while ( cur )
> {
>     *p++ =3D ( number & cur ) ? '1' : '0';
>     cur >>=3D 1;
> }
> *p =3D '\0';
>=20
> Things get a tiny bit more complicted when you don't want leading
> zeros, but that shouldn't be too difficult to figure out...
>=20
>                                        Regards, Jens

Actually, I've found that a lookup table consisting of
16 entries (assuming that char is 8 bits) works a lot
faster.  Convert the single char in the hex string to some int=20
representation (e.g. 'f' or 'F' converts to 15) and use that
as in index into the lookup table, which has an array
of strings ( char *table[] ) with binary
representation for that hex character as a null terminated
string.




--=20
=D1
"It is impossible to make anything foolproof because fools are so=20
ingenious" - A. Bloch

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