define a data type of 1 bit size

[Angel Lopez]

Sorry if this appears twice but my first try didn't seem to make it.
but this is my first post (hopefully)...
I have a binary variable (it can contain either a 0 or a 1).
Is there any way I can define a data type that uses only 1 bit. So
far I have defined it as a char variable. I've searched everywhere but
I don't seem to find any place that explains how to define this type
of data type. The closest thing I've found are bit fields in
structures, I would like something like bit fields but without the
structure.
something like
unsigned MyVariable :1;
Thanks,
Angel

 

[Martin Ambuhl]

Sorry if this appears twice but my first try didn't seem to make it.
but this is my first post (hopefully)...
I have a binary variable (it can contain either a 0 or a 1).
Is there any way I can define a data type that uses only 1 bit.

No. The smallest data type is the char, which is guaranteed to be at
least 8 bits.

You can use bit-masking on an unsigned integral type (unsigned char,
unsigned short, unsigned int, unsigned long, unsigned long long) or you
can use bitfields in a structure if you want.

So
far I have defined it as a char variable. I've searched everywhere but
I don't seem to find any place that explains how to define this type
of data type.

see above.

 

[Kelsey Bjarnason]

[snips]

Sorry if this appears twice but my first try didn't seem to make it.
but this is my first post (hopefully)...
I have a binary variable (it can contain either a 0 or a 1).
Is there any way I can define a data type that uses only 1 bit.

I seem to recall having worked with a compiler, years ago, that supported
a "bit" type... but that's totally non-portable, even to other compilers
on the same platform.

Probably the easiest is to just use unsigned chars or unsigned ints and a
function or two; it's not that hard to test to see if a given bit is set,
or to set or clear it.

Example: suppose we want to work with, oh, 500 bits, we might do something
like this:

unsigned char bitbuff[(500+(CHAR_BIT-1))/CHAR_BIT];

void setbit( unsigned bit, unsigned state )
{
unsigned byte = bit / CHAR_BIT;
bit %= CHAR_BIT;

bitbuff[byte] &= ~(1 << bit ); /* turns bit off */
if ( state )
bitbuff[byte] |= (1 << bit ); /* turn on if necessary */
}


It's morning, and I haven't had my coffee yet, so it may not be spot on,
but the concept should work.

 

[Merrill & Michele]

[snips]

Sorry if this appears twice but my first try didn't seem to make it.
but this is my first post (hopefully)...
I have a binary variable (it can contain either a 0 or a 1).
Is there any way I can define a data type that uses only 1 bit.

I seem to recall having worked with a compiler, years ago, that supported
a "bit" type... but that's totally non-portable, even to other compilers
on the same platform.

Probably the easiest is to just use unsigned chars or unsigned ints and a
function or two; it's not that hard to test to see if a given bit is set,
or to set or clear it.

Example: suppose we want to work with, oh, 500 bits, we might do something
like this:

unsigned char bitbuff[(500+(CHAR_BIT-1))/CHAR_BIT];

void setbit( unsigned bit, unsigned state )
{
unsigned byte = bit / CHAR_BIT;
bit %= CHAR_BIT;

bitbuff[byte] &= ~(1 << bit ); /* turns bit off */
if ( state )
bitbuff[byte] |= (1 << bit ); /* turn on if necessary */
}


It's morning, and I haven't had my coffee yet, so it may not be spot on,
but the concept should work.

But is this bit an ANSI c data type? MPJ

 

[c453___]

if u really want to be economic with process's memory u can use for
example a char (or int) and store in it up to 8 (or 32) one bit values

 

[Christopher Benson-Manica]

if u really want to be economic with process's memory u can use for
example a char (or int) and store in it up to 8 (or 32) one bit values

You mean CHAR_BIT or sizeof( int )*CHAR_BIT.