how to print it out

[poison.summer]

Hi I have a char p,
I'd like to print out the lower 4 bits and higher 4 bits of p
seperately
how can i do that?
Thanks a lot!

[Rod Pemberton]

<po***********@ gmail.com> wrote in message
news:11******** **************@ g14g2000cwa.goo glegroups.com.. .

Hi I have a char p,
I'd like to print out the lower 4 bits and higher 4 bits of p
seperately
how can i do that?
Thanks a lot!

I prefer to setup tables, but you don't need to. If you want a simpler
method, the logic that setup_bin_tab uses to setup the string table can be
used without a table. nyb_l is short for nybble_lower, etc. (If you
understand hexadecimal, you can determine the bit patterns in your head.)

Rod Pemberton

//--working--code--

#include <stdio.h>
#include <string.h>

#define nyb_l(a) ((a)&0x0F)
#define nyb_u(a) (((a)>>4)&0x0F)

unsigned char bin_tab[16][5];

void setup_bin_tab(v oid)
{
unsigned char i,j;

/* set nul's for EOS */
memset(bin_tab, 0,sizeof(bin_ta b));

for(i=0;i<16;i+ +)
{
for(j=0;j<4;j++ )
{
bin_tab[i][j]=(i&(1<<(3-j)))?'1':'0';
}
}
}
int main(void)
{
unsigned char p;

setup_bin_tab() ;

p=0x82;
printf("%02x %s %s\n",p,bin_tab[nyb_u(p)],bin_tab[nyb_l(p)]);

p=0x5A;
printf("%02x %s %s\n",p,bin_tab[nyb_u(p)],bin_tab[nyb_l(p)]);

return(0);
}

[Pedro Graca]

po***********@g mail.com wrote:

Hi I have a char p,
I'd like to print out the lower 4 bits and higher 4 bits of p
seperately
how can i do that?
Thanks a lot!

#include <stdio.h>

int main(void) {
unsigned char p = 42; /* or whatever */
char hibits[5] = {'0', '0', '0', '0', 0};
char lobits[5] = {'0', '0', '0', '0', 0};

if (p > 127) {
hibits[0] = '1';
p -= 128;
}
if (p > 63) {
hibits[1] = '1';
p -= 64;
}
if (p > 31) {
hibits[2] = '1';
p -= 32;
}
if (p > 15) {
hibits[3] = '1';
p -= 16;
}
if (p > 7) {
lobits[0] = '1';
p -= 8;
}
if (p > 3) {
lobits[1] = '1';
p -= 4;
}
if (p > 1) {
lobits[2] = '1';
p -= 2;
}
if (p == 1) {
lobits[3] = '1';
}
printf("Hibits: %s\n", hibits);
printf("Lobits: %s\n", lobits);
return 0;
}

--
If you're posting through Google read <http://cfaj.freeshell. org/google>

[Joe Wright]

po***********@g mail.com wrote:

Hi I have a char p,
I'd like to print out the lower 4 bits and higher 4 bits of p
seperately
how can i do that?
Thanks a lot!

I give up, how can you? How do you want to print the bits? What problems
do you have when you try it? Talk to me. Show me some C code.

--
Joe Wright
"Everything should be made as simple as possible, but not simpler."
--- Albert Einstein ---

[stathis gotsis]

"Rod Pemberton" <do*********@so rry.bitbucket.c mm> wrote in message
news:dt******** **@news1.greatn owhere.com...

<po***********@ gmail.com> wrote in message
news:11******** **************@ g14g2000cwa.goo glegroups.com.. .

Hi I have a char p,
I'd like to print out the lower 4 bits and higher 4 bits of p
seperately Rod Pemberton

//--working--code--

#include <stdio.h>
#include <string.h>

#define nyb_l(a) ((a)&0x0F)
#define nyb_u(a) (((a)>>4)&0x0F)

Is char restricted to 8 bits? If not, maybe this is more general:

#define nyb_u(a) (((a)>>(sizeof( a)*8-4))&0x0F)

unsigned char bin_tab[16][5];

void setup_bin_tab(v oid)
{
unsigned char i,j;

/* set nul's for EOS */
memset(bin_tab, 0,sizeof(bin_ta b));

for(i=0;i<16;i+ +)
{
for(j=0;j<4;j++ )
{
bin_tab[i][j]=(i&(1<<(3-j)))?'1':'0';
}
}
}
int main(void)
{
unsigned char p;

setup_bin_tab() ;

p=0x82;
printf("%02x %s %s\n",p,bin_tab[nyb_u(p)],bin_tab[nyb_l(p)]);

p=0x5A;
printf("%02x %s %s\n",p,bin_tab[nyb_u(p)],bin_tab[nyb_l(p)]);

return(0);
}

[Jack Klein]

On Tue, 21 Feb 2006 05:00:19 +0200, "stathis gotsis"
<st***********@ hotmail.com> wrote in comp.lang.c:

"Rod Pemberton" <do*********@so rry.bitbucket.c mm> wrote in message
news:dt******** **@news1.greatn owhere.com...

<po***********@ gmail.com> wrote in message
news:11******** **************@ g14g2000cwa.goo glegroups.com.. .

Hi I have a char p,
I'd like to print out the lower 4 bits and higher 4 bits of p
seperately Rod Pemberton

//--working--code--

#include <stdio.h>
#include <string.h>

#define nyb_l(a) ((a)&0x0F)
#define nyb_u(a) (((a)>>4)&0x0F)

Is char restricted to 8 bits? If not, maybe this is more general:

No, char is not restricted to 8 bits, it can't be less buy may be
more. I routinely work on C implementations for DSPs where chars have
16 or 32 bits. The macro CHAR_BIT in <limits.h> gives the number of
bits.
#define nyb_u(a) (((a)>>(sizeof( a)*8-4))&0x0F)

Uh, no, while char is not limited to 8 bits, it is limited to being
exactly one byte. sizeof(char) is 1 by definition in C, always has
been, always will be. Even if char contains more than one octet,
which is the proper term for a collection of exactly 8 bits.

So your expression is exactly equivalent to Rod's.

If you want to be truly portable and get the lowest 4 bits and highest
4 bits out of a character, you need to do this:

#define myb_u(a) (((a)>>(CHAR_BI T-4))&0x0f)

....if I counted the parentheses correctly.

On a Texas Instruments TMS320F2812, that would give you bits 15
through 12 of the 16-bit char.

--
Jack Klein
Home: http://JK-Technology.Com
FAQs for
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alt.comp.lang.l earn.c-c++
http://www.contrib.andrew.cmu.edu/~a...FAQ-acllc.html

[Keith Thompson]

Jack Klein <ja*******@spam cop.net> writes:

On Tue, 21 Feb 2006 05:00:19 +0200, "stathis gotsis"
<st***********@ hotmail.com> wrote in comp.lang.c:

[...]

Is char restricted to 8 bits? If not, maybe this is more general:

No, char is not restricted to 8 bits, it can't be less buy may be
more. I routinely work on C implementations for DSPs where chars have
16 or 32 bits. The macro CHAR_BIT in <limits.h> gives the number of
bits.

#define nyb_u(a) (((a)>>(sizeof( a)*8-4))&0x0F)

Uh, no, while char is not limited to 8 bits, it is limited to being
exactly one byte. sizeof(char) is 1 by definition in C, always has
been, always will be. Even if char contains more than one octet,
which is the proper term for a collection of exactly 8 bits.

So your expression is exactly equivalent to Rod's.

Except that character constants are of type int, so nyb_u('x') will
use sizeof('x'), which is the same as sizeof(int). You probably
don't want to apply sizeof to the argument.

--
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.

[pete]

Jack Klein wrote:

If you want to be truly portable and get the lowest 4 bits and highest
4 bits out of a character, you need to do this:

#define myb_u(a) (((a)>>(CHAR_BI T-4))&0x0f)

I don't think that mask does anything.

--
pete

[stathis gotsis]

"Jack Klein" <ja*******@spam cop.net> wrote in message
news:39******** *************** *********@4ax.c om...

On Tue, 21 Feb 2006 05:00:19 +0200, "stathis gotsis"
<st***********@ hotmail.com> wrote in comp.lang.c:

"Rod Pemberton" <do*********@so rry.bitbucket.c mm> wrote in message
news:dt******** **@news1.greatn owhere.com...

<po***********@ gmail.com> wrote in message
news:11******** **************@ g14g2000cwa.goo glegroups.com.. .
> Hi I have a char p,
> I'd like to print out the lower 4 bits and higher 4 bits of p
> seperately
Rod Pemberton

//--working--code--

#include <stdio.h>
#include <string.h>

#define nyb_l(a) ((a)&0x0F)
#define nyb_u(a) (((a)>>4)&0x0F)

Is char restricted to 8 bits? If not, maybe this is more general:

No, char is not restricted to 8 bits, it can't be less buy may be
more. I routinely work on C implementations for DSPs where chars have
16 or 32 bits. The macro CHAR_BIT in <limits.h> gives the number of
bits.

#define nyb_u(a) (((a)>>(sizeof( a)*8-4))&0x0F)

Uh, no, while char is not limited to 8 bits, it is limited to being
exactly one byte. sizeof(char) is 1 by definition in C, always has
been, always will be. Even if char contains more than one octet,
which is the proper term for a collection of exactly 8 bits.

Yes that is correct, terrible confusion. Thank you for the correction. I
should have used CHAR_BIT instead.

[stathis gotsis]

"Jack Klein" <ja*******@spam cop.net> wrote in message
news:39******** *************** *********@4ax.c om...

Uh, no, while char is not limited to 8 bits, it is limited to being
exactly one byte. sizeof(char) is 1 by definition in C, always has
been, always will be. Even if char contains more than one octet,
which is the proper term for a collection of exactly 8 bits.

I am having second thoughts (or rather questions) about this. I am aware of
implementations which have 16 or 32-bit bytes and sizeof(char)==1 . But does
the Standard explicitly state that char must be one byte?