Simple C question...entering binary

Started by Thomas Magma January 18, 2008
Quick question.

How do you enter a literal in binary? That is, the binary equivalent of:

x = 0xFFFF //hex entry

Thank,
Thomas


Thomas Magma wrote:
> Quick question. > > How do you enter a literal in binary? That is, the binary equivalent of: > > x = 0xFFFF //hex entry
x = 0xFFFF; I have seen some compilers with non-standard extensions that allow the similar form x = 0b11111111; but that IS non-standard. Probably if one really, really wanted to do that, the source could be run through a Perl or awk filter before handing it off to the pre-processor. Also once saw (and was amazed by) a page of pre-processor macros that took a "binary" argument and emitted the equivalent hex form. -- Rich Webb Norfolk, VA
> > x = 0b11111111; >
The C30 compiler excepted that, thanks. (I'm programming a dsPIC for the first time and I like to set my TRIS register values in binary.) Thanks Rich.
Thomas Magma wrote:
> How do you enter a literal in binary? That is, the binary equivalent of: > > x = 0xFFFF //hex entry
You translate it to hex and use that :-) Or, you define mnemonic names for the actual bits you're using and use these in an expression, as in GCTL = TXEN | RXEN | STOP_BIT | WORD_SIZE_8 instead of GCTL = 0b00110101; (register names have been made up). That aside, the preprocessor magic version is a variation of #define BINARY_OCTET(x) \ (((0##x & 01)) | \ ((0##x & 010) >> 2) | \ ((0##x & 0100) >> 4) | \ ((0##x & 01000) >> 6) | \ ((0##x & 010000) >> 8) | \ ((0##x & 0100000) >> 10) | \ ((0##x & 01000000) >> 12) | \ ((0##x & 010000000) >> 14)) int main() { printf("%x\n", BINARY_OCTET(10100100)); return 0; } It's fun for its hack value, but I wouldn't want it in production code. Stefan
"Thomas Magma"  wrote:
>How do you enter a literal in binary? That is, the binary equivalent of: >x = 0xFFFF //hex entry
There is a clever set of macros from Tom Torfs to do this. See: http://www.velocityreviews.com/forums/t317511-binary-constant-macros.html Roberto Waltman [ Please reply to the group, return address is invalid ]
Thomas Magma wrote:
> > How do you enter a literal in binary? That is, the binary > equivalent of: x = 0xFFFF //hex entry
You can enter the value in hex, octal, or decimal. For example: unsigned int x; .... x = 0xffff; /* or */ x = 0177777; /* or */ x = 65535U; /* or */ x = 0170000 + 0xf00 + 255U; -- [mail]: Chuck F (cbfalconer at maineline dot net) [page]: <http://cbfalconer.home.att.net> Try the download section. -- Posted via a free Usenet account from http://www.teranews.com
On Fri, 18 Jan 2008 21:08:21 +0100, Stefan Reuther
<stefan.news@arcor.de> wrote:

>That aside, the preprocessor magic version is a variation of > #define BINARY_OCTET(x) \ > (((0##x & 01)) | \ > ((0##x & 010) >> 2) | \ > ((0##x & 0100) >> 4) | \ > ((0##x & 01000) >> 6) | \ > ((0##x & 010000) >> 8) | \ > ((0##x & 0100000) >> 10) | \ > ((0##x & 01000000) >> 12) | \ > ((0##x & 010000000) >> 14)) > > int main() { > printf("%x\n", BINARY_OCTET(10100100)); > return 0; > } >It's fun for its hack value, but I wouldn't want it in production code.
Why not. I'd say a decent compiler will just calculate it at compile time. -- 42Bastian Do not email to bastian42@yahoo.com, it's a spam-only account :-) Use <same-name>@monlynx.de instead !
"Thomas Magma" <somewhere@overtherainbow.com> skrev i meddelandet 
news:Yw7kj.100328$EA5.10420@pd7urf2no...
> > >> x = 0b11111111; >> > > The C30 compiler excepted that, thanks. (I'm programming a dsPIC for the > first time and I like to set my TRIS register values in binary.) > > Thanks Rich. > >
And here is the ANSI C compatible way. #define BIT(n) (1 << n) #define BIT0 BIT(0) #define BIT1 BIT(1) #define BIT2 BIT(2) #define BIT3 BIT(3) #define BIT4 BIT(4) #define BIT5 BIT(5) #define BIT6 BIT(6) #define BIT7 BIT(7) TRIS = BIT7 | BIT3 | BIT0; -- Best Regards, Ulf Samuelsson This is intended to be my personal opinion which may, or may not be shared by my employer Atmel Nordic AB
In article <47914AAB.E10DFAB8@yahoo.com>,
CBFalconer  <cbfalconer@maineline.net> wrote:
>Thomas Magma wrote: >> >> How do you enter a literal in binary? That is, the binary >> equivalent of: x = 0xFFFF //hex entry > >You can enter the value in hex, octal, or decimal. For example: > > unsigned int x; > .... > x = 0xffff; >/* or */ x = 0177777; >/* or */ x = 65535U; >/* or */ x = 0170000 + 0xf00 + 255U;
And the most convenient of all x = -1; (For those not in the know, the definition of unsigned explicitly makes this works. There may be an additional advantage that it ports over to 64 bits more easily.) And of course: x = ~0;
> >-- > [mail]: Chuck F (cbfalconer at maineline dot net) > [page]: <http://cbfalconer.home.att.net> > Try the download section. > > > >-- >Posted via a free Usenet account from http://www.teranews.com >
-- -- Albert van der Horst, UTRECHT,THE NETHERLANDS Economic growth -- like all pyramid schemes -- ultimately falters. albert@spe&ar&c.xs4all.nl &=n http://home.hccnet.nl/a.w.m.van.der.horst
Albert van der Horst wrote:
> CBFalconer <cbfalconer@maineline.net> wrote: >> Thomas Magma wrote: >>> >>> How do you enter a literal in binary? That is, the binary >>> equivalent of: x = 0xFFFF //hex entry >> >> You can enter the value in hex, octal, or decimal. For example: >> >> unsigned int x; >> .... >> x = 0xffff; >> /* or */ x = 0177777; >> /* or */ x = 65535U; >> /* or */ x = 0170000 + 0xf00 + 255U; > > And the most convenient of all > x = -1; > > (For those not in the know, the definition of unsigned > explicitly makes this works. There may be an additional > advantage that it ports over to 64 bits more easily.)
Depends on the objective. x = -1 will create the maximum unsigned value possible (which might be 0xffffffff on some machines). The sequences I showed will create 0xffff, regardless of the size of the int. -- [mail]: Chuck F (cbfalconer at maineline dot net) [page]: <http://cbfalconer.home.att.net> Try the download section. -- Posted via a free Usenet account from http://www.teranews.com