-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
The Saturday 2007-01-20 at 14:41 -0600, Greg Wallace wrote:
> >> > > than the full-size "word" of most architectures of the time.
> >> > > And some architectures do allow you direct access to a bit.
> >>
> >> Why only some?
> >> Aren't shift- and logical operations part of all CPU architectures?
>
> >That's not direct access to a bit, IMO. Direct access would be an
> >operation that would load into a register a certain bit, or another that
> >would compare directly to a certain bit in a byte in memory (in one op). I
> >have never seen it, though.
>
> Well, on the second point I think there is the capability of doing a compare
> under mask where you mask all of the bits except the one you want to compare
> against. You still load a full word into memory though, even though you're
> only comparing against one bit. At least that's the way I understand it.
Not quite, using masks we still operate on the full byte or word. It's a
logic trick, only the "target" bit will modify the output. But the
operation is on the whole.
That is, we can make decissions based on the state of a certain bit, for
instance, but the procesor can not directly access a bit.
- --
Cheers,
Carlos E. R.
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.2 (GNU/Linux)
Comment: Made with pgp4pine 1.76
iD8DBQFFsrbjtTMYHG2NR9URAqNWAJ9N5barBTZ3OFXAAoB5B3Do0NRMgACaAygO
BrwbHiB5nhN+HNOY1TM08GM=
=shgR
-----END PGP SIGNATURE-----
--
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
