From:	"Tim Nicholson" <T DOT J DOT Nicholson AT btinternet DOT com>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Bit field query
Date:	Thu, 4 Oct 2001 21:26:34 +0100
Organization:	Skyforce avionics Limited
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Message-ID:	<9pigq7$art$1@uranium.btinternet.com>
References:	<9pidst$kgu$1 AT epos DOT tesco DOT net> <9pigh8$abp$1 AT uranium DOT btinternet DOT com>
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To:	djgpp AT delorie DOT com
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Reply-To:	djgpp AT delorie DOT com

Correction, it appears in the right most bit! - Sorry, I knew I should put L
& R on my boots ;-)

Tim

"Tim Nicholson" <T DOT J DOT Nicholson AT btinternet DOT com> wrote in message
news:9pigh8$abp$1 AT uranium DOT btinternet DOT com...
> B0 is the LSB and apears in the leftmost bit of the 32 bit field. The
> following program will prove this.
>
> Tim
>
> //Compile this to show the bit field.
>
> struct bit_field
> {
> unsigned int b0 : 1;
> unsigned int b1 : 1;
> unsigned int b2 : 1;
> unsigned int b3 : 1;
> unsigned int b4 : 1;
> unsigned int b5 : 1;
> unsigned int b6 : 1;
> unsigned int b7 : 1;
> };
>
> int main(void)
> {
> struct bit_field my_bits;
> unsigned int *my_word;
> short int i;
>
> my_word = (unsigned int *) &my_bits;
>
> *my_word = 0;
>
> my_bits.b0 = 1;
> my_bits.b5 = 1;
> for (i=0; i<32;i++)
>    {
>    printf("%d", (*my_word) & 0x80000000 ? 1:0);
>    *my_word <<= 1;
>    }
> printf("\n");
> }
> "Graham Warren" <Moosehead AT tesco DOT net> wrote in message
> news:9pidst$kgu$1 AT epos DOT tesco DOT net...
> > I have a question about bit-fields.
> >
> > In a program I have defined a bit-field using the code shown below.
> >
> >
> > /* define bit-field */
> >
> > struct {
> > unsigned int b0 : 1;
> > unsigned int b1 : 1;
> > unsigned int b2 : 1;
> > unsigned int b3 : 1;
> > unsigned int b4 : 1;
> > unsigned int b5 : 1;
> > unsigned int b6 : 1;
> > unsigned int b7 : 1;
> > } bit_field;
> >
> > /* */
> >
> >
> >
> > My questions are: would bit_field.b0 be the furthest left or furthest
> right
> > bit if the byte is written out 00000000?
> > Would this change if more bits were defined in the bit field to make it
> > spill over into a larger than 1 byte area?
> >
> > Also which bit in 00000000 is referred to as the most-significant and
> which
> > is the least-significant?
> >
> >
> > Thankyou
> > Graham Warren
> >
> >
>
>

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