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In article ghm@bcarh8ab.bnr.ca, "brian (b.c.) white" <bcwhite@bnr.ca> writes:
>
>I thought I read somewhere that C++ guarantees a "char" to be 8 bits (or
>was that "one byte"?).

In C and C++, the size of a char or a byte is always implementation-defined,
and neither is required to be exactly 8 bits. A char or a byte could have more
(or fewer) than 8 bits.

Excerpts from the C++ draft standard:

[intro.memory]  1.5 The C++ memory model
The fundamental storage unit in the C++ memory model is the byte. A byte is
at least large enough to contain any member of the basic execution character
set and is composed of a contiguous sequence of bits, the number of which
is implementation­defined.  ...

[basic.fundamental]  3.9.1 Fundamental types
Objects declared as characters (char) shall be large enough to store any
member of the implementation's basic character set.  ...  
---
Steve Clamage, stephen.clamage@eng.sun.com




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: In article ghm@bcarh8ab.bnr.ca, "brian (b.c.) white" <bcwhite@bnr.ca> writes:
: >I thought I read somewhere that C++ guarantees a "char" to be 8 bits (or
: >was that "one byte"?).

Steve Clamage (clamage@Eng.Sun.COM) responded:
: In C and C++, the size of a char or a byte is always implementation-defined,
: and neither is required to be exactly 8 bits. A char or a byte could have more
: (or fewer) than 8 bits.
: [snip, standard reference]

Right--remember back to the old C days?  A "byte" was defined
to be a sizeof() of ONE, and all other data types were based on
multiples of ONE.  (An "int" was TWO on MS-DOS platforms, or
FOUR on UNIX platforms, etc.)  The platform determined exactly what
that ONE was, and the source code was never supposed to care.

This was a major boon for portability (although I acknowledge
it's harder to guess ranges).

--
--charley                              #include <stdisclaimer.h>
charleyb@gr.hp.com    -or-    charley@agrostis.nrel.colostate.edu



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"brian (b.c.) white" <bcwhite@bnr.ca> wrote:

[ ... ]
>I thought I read somewhere that C++ guarantees a "char" to be 8 bits (or
>was that "one byte"?).

One byte.  The number of bits in a char can be found in limits.h as
CHAR_BIT. (Actually, the current name is something like climitsh instead
of limits.h)
    Later,
    Jerry.

/* I can barely express my own opinions; I certainly can't
 * express anybody else's.
 *
 * The universe is a figment of its own imagination.
 */


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Steve Clamage (clamage@Eng.Sun.COM) wrote:
: In C and C++, the size of a char or a byte is always implementation-defined,
: and neither is required to be exactly 8 bits. A char or a byte could have more
: (or fewer) than 8 bits.

Isn't CHAR_BITS (in limits.h) required to be at least 8 (with the
obvious implication that char is at least 8 bits)?
-- 
        Tony Cook - tony@online.tmx.com.au
                    100237.3425@compuserve.com

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tony@online.tmx.com.au (Tony Cook) wrote:

[ ... ] 
>Isn't CHAR_BITS (in limits.h) required to be at least 8 (with the
>obvious implication that char is at least 8 bits)?

Yes.  (or more accurately, it's CHAR_BIT, but...)  Anyhow, there's more
than an implication involved.  The C standard specifically says "number
of bits for the smallest object that is not a bit-field"...
    Later,
    Jerry.

/* I can barely express my own opinions; I certainly can't
 * express anybody else's.
 *
 * The universe is a figment of its own imagination.
 */


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