Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.programming > #5101

Re: 64-bit bytes

Show all headers | View raw

On 12/01/2015 14:15, Ben Bacarisse wrote:
> Mark Carroll <mtbc@bcs.org> writes:

>> Exactly. For instance, Erlang, being designed to run on various odd
>> computer architectures, lets one ask,
>>
>> 	erlang:system_info(wordsize)
>>
>> which is documented as,
>>
>> ] Returns the size of Erlang term words in bytes as an integer, i.e. on
>> ] a 32-bit architecture 4 is returned, and on a pure 64-bit architecture
>> ] 8 is returned.
>>
>> which clearly implies 8-bit bytes.
>
> I would not call 32-bit and 64-bit architectures "odd"!  What would it
> do on a 36-bit or a 60-bit machine?

At the time the language was created (1986 according to Wikipedia), it 
must already have been clear that the machine word sizes the language 
would be likely to run on, would be 16 or 32 or 64 bits. In other words, 
be based on powers-of-two and therefore multiples of a byte.

This is unlike C which is still (even now) expected to work on all sorts 
of genuinely odd microprocessor architectures.

(BTW what would C's sizeof(int) return on a 36-bit or 60-bit machine?)

> Not knowing anything about Erlang I'm curious about the need to make any
> assumption about bytes at all.  Why does the function not return the
> number of value bits?  Surely that's both more flexible an just as
> useful?

The number of bytes must be more useful overall, it you wished to find 
out how much RAM is taken up by N words, or how much disk space, or the 
size of a record; you rarely do these calculation in bits.

You can derive a byte-count from the number of bits, but this is an 
extra, inconvenient step. And you might then be obliged to consider the 
possibility of a byte-width not dividing exactly into the word size, or 
explaining why you've hard-coded a divide-by-eight into a calculation! 
It just more untidy.

Anyway after nearly 30 years, it doesn't sound as though it's done the 
language much harm.

-- 
Bartc

Back to comp.programming | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

64-bit bytes fir <profesor.fir@gmail.com> - 2015-01-05 01:38 -0800
  Re: 64-bit bytes robin.vowels@gmail.com - 2015-01-08 00:46 -0800
    Re: 64-bit bytes fir <profesor.fir@gmail.com> - 2015-01-08 00:53 -0800
      Re: 64-bit bytes robin.vowels@gmail.com - 2015-01-11 15:46 -0800
        Re: 64-bit bytes Richard Heathfield <invalid@see.sig.invalid> - 2015-01-12 00:32 +0000
          Re: 64-bit bytes BartC <bc@freeuk.com> - 2015-01-12 01:35 +0000
            Re: 64-bit bytes Richard Heathfield <invalid@see.sig.invalid> - 2015-01-12 09:07 +0000
              Re: 64-bit bytes BartC <bc@freeuk.com> - 2015-01-12 11:43 +0000
                Re: 64-bit bytes Richard Heathfield <invalid@see.sig.invalid> - 2015-01-12 11:59 +0000
                Re: 64-bit bytes BartC <bc@freeuk.com> - 2015-01-12 12:21 +0000
                Re: 64-bit bytes Mark Carroll <mtbc@bcs.org> - 2015-01-12 12:36 +0000
                Re: 64-bit bytes Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-01-12 14:15 +0000
                Re: 64-bit bytes BartC <bc@freeuk.com> - 2015-01-12 14:34 +0000
                Re: 64-bit bytes "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2015-01-12 16:35 +0100
                Re: 64-bit bytes BartC <bc@freeuk.com> - 2015-01-12 17:42 +0000
                Re: 64-bit bytes "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2015-01-12 19:11 +0100
                Re: 64-bit bytes BartC <bc@freeuk.com> - 2015-01-12 19:18 +0000
                Re: 64-bit bytes "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2015-01-12 21:34 +0100
                Re: 64-bit bytes BartC <bc@freeuk.com> - 2015-01-12 22:01 +0000
                Re: 64-bit bytes Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-01-13 00:51 +0000
                Re: 64-bit bytes Richard Heathfield <invalid@see.sig.invalid> - 2015-01-12 13:18 +0000
                Re: 64-bit bytes BartC <bc@freeuk.com> - 2015-01-12 14:16 +0000
                Re: 64-bit bytes Richard Heathfield <invalid@see.sig.invalid> - 2015-01-12 14:48 +0000
                Re: 64-bit bytes BartC <bc@freeuk.com> - 2015-01-12 15:05 +0000
                Re: 64-bit bytes Robert Wessel <robertwessel2@yahoo.com> - 2015-01-12 15:43 -0600
              Re: 64-bit bytes Kaz Kylheku <kaz@kylheku.com> - 2015-01-12 21:05 +0000
                Re: 64-bit bytes Richard Heathfield <invalid@see.sig.invalid> - 2015-01-12 22:12 +0000
            Re: 64-bit bytes "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2015-01-12 10:12 +0100
          Re: 64-bit bytes robin.vowels@gmail.com - 2015-01-11 20:56 -0800
            Re: 64-bit bytes Richard Heathfield <invalid@see.sig.invalid> - 2015-01-12 09:19 +0000
              Re: 64-bit bytes robin.vowels@gmail.com - 2015-01-12 06:22 -0800
                Re: 64-bit bytes Richard Heathfield <invalid@see.sig.invalid> - 2015-01-12 14:51 +0000
                Re: 64-bit bytes robin.vowels@gmail.com - 2015-01-12 15:46 -0800
                Re: 64-bit bytes Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-01-13 01:16 +0000
                Re: 64-bit bytes Richard Heathfield <invalid@see.sig.invalid> - 2015-01-13 01:53 +0000
                Re: 64-bit bytes Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-01-13 13:28 +0000
                Re: 64-bit bytes Richard Heathfield <invalid@see.sig.invalid> - 2015-01-13 13:57 +0000
                Re: 64-bit bytes "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> - 2015-01-13 15:32 +0100
                Re: 64-bit bytes fir <profesor.fir@gmail.com> - 2015-01-13 06:33 -0800
                Re: 64-bit bytes BartC <bc@freeuk.com> - 2015-01-13 16:41 +0000
                Re: 64-bit bytes fir <profesor.fir@gmail.com> - 2015-01-13 15:25 -0800
                Re: 64-bit bytes BartC <bc@freeuk.com> - 2015-01-13 23:49 +0000
                Re: 64-bit bytes fir <profesor.fir@gmail.com> - 2015-01-13 23:57 -0800

csiph-web