[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
RE: [avr-gcc-list] 24 bit Integer
From: |
Dave Hansen |
Subject: |
RE: [avr-gcc-list] 24 bit Integer |
Date: |
Thu, 31 Jul 2008 00:46:12 -0400 |
For a PDP-8, CHAR_BIT would be 12, int could have 24 bits, and long could have
36 or 48, whatever is most convenient/efficient/desired.
For a PDP-15, char and int could be the same 18-bit type, and long could be 36
bits.
On further reflection, you might be able to replace the standard 16 bit int on
AVR with a 24 bit int. The required ranges are minimums. That makes int16_t a
special type outside the normal hierarchy, however, and I'm not certain that's
allowed.
Regards,
-=Dave
________________________________
From: address@hidden
[...]
what about a PDP 8 or PDP 15, could we not code for it? being 12 and 18 bit
machines?
From: address@hidden
> 2008/7/14 Weddington, Eric <address@hidden>:
>> A 24-bit integer is not supported by the C language. In theory, support
>> could be added to GCC, but then it would be considered an extension to
>> the C language. And it would also be difficult and/or time-consuming to
>> add to GCC.
>
> The C standard doesn't dictate the size of any integer type, except that char
> must be large enough to hold the environments standard character set and
> the size of any larger types is ordered as you'd expect.
> char <= short <= int <= long
Also that short and int must be able to represent at least -32767 to +32767,
and long must be able to represent +/-2,147,483,647. So int24_t would have to
be a special type outside the standard types.
And I think (though I'm not certain) that it would have to be promoted to long
before any operator could be applied. Some of that would be mitigated by the
as-if rule, of course...
> int is typically the natural word size for the architecture, but often on 8
> bit
> micros it will be larger (since char typically provides an 8 bit int anyway.)
It's larger because an 8 bits can't represent the required range of values.
Regards,
-=Dave
________________________________
Time for vacation? WIN what you need. Enter Now!
_______________________________________________
AVR-GCC-list mailing list
address@hidden
http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
_________________________________________________________________
With Windows Live for mobile, your contacts travel with you.
http://www.windowslive.com/mobile/overview.html?ocid=TXT_TAGLM_WL_mobile_072008
- [avr-gcc-list] 24 bit Integer, Moritz Struebe, 2008/07/14
- RE: [avr-gcc-list] 24 bit Integer, Weddington, Eric, 2008/07/14
- Re: [avr-gcc-list] 24 bit Integer, David Kelly, 2008/07/14
- Re: [avr-gcc-list] 24 bit Integer, Clint Lawrence, 2008/07/30
- RE: [avr-gcc-list] 24 bit Integer, Dave Hansen, 2008/07/30
- Re: [avr-gcc-list] 24 bit Integer, Steven Michalske, 2008/07/30
- RE: [avr-gcc-list] 24 bit Integer, Weddington, Eric, 2008/07/30
- Re: [avr-gcc-list] 24 bit Integer, Steven Michalske, 2008/07/31
- Re: [avr-gcc-list] 24 bit Integer, Dave N6NZ, 2008/07/31
- RE: [avr-gcc-list] 24 bit Integer,
Dave Hansen <=
- RE: [avr-gcc-list] 24 bit Integer, Stu Bell, 2008/07/31