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Re: Can Java compute 9^(9^9) ?

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On 6/10/2018 5:31 AM, bursejan@gmail.com wrote:
> Am Sonntag, 10. Juni 2018 11:13:19 UTC+2 schrieb Martin Gregorie:
>> On Sat, 09 Jun 2018 23:29:53 +0000, Volker Borchert wrote:
>>> j4n bur53 wrote:
>>>> Interestingly IBM, also for their new POWER9,
>>>> still provides BCD coding support.
>>>
>>> Is it part of ANSI COBOL?
>>>
>> Its been a long time since I wrote any COBOL, and I've never done so on
>> IBM kit [only ICL 1900 (24bit word, 6bit char), ICL 2900 (byte-oriented),
>> DEC VAX, Tandem and NCR UNIX (Intel chips)] and AFAIK none of these
>> machines supported BCD arithmetic at the hardware level.
>>
>> COBOL specifies a number of numeric representations which include COMP
>> (fixed length numeric strings), DISPLAY (formatted character strings)
>> COMP SYNC (native binary representations) and a few others (COMP-n)
>> including floating point. I think you'll find that the internal
>> representation of COMP variables is undefined by the standard as long as
>> manipulating it works to the CODSASYL rules. I've looked at COBOL crash
>> dumps on most of these systems and don't recall any of them using some
>> form of non-native numeric storage, i.e. if you could read the assembler,
>> the data division of the COBOL dump was understandable.
> 
> Intel 8080 had hardware support for BCD arithmetic
> https://en.wikipedia.org/wiki/Half-carry_flag
> 
> While packed BCD does not make optimal use
> of storage (about one-sixth of the memory used
> is wasted), conversion to ASCII, EBCDIC, or
> the various encodings of Unicode is still
> trivial, as no arithmetic operations are
> required. The extra storage requirements
> are usually offset by the need for the
> accuracy and compatibility with calculator
> or hand calculation that fixed-point decimal
> arithmetic provides. Denser packings of BCD
> exist which avoid the storage penalty and
> also need no arithmetic operations for
> common conversions.
> 
> Packed BCD is supported in the COBOL programming
> language as the "COMPUTATIONAL-3" (an IBM
> extension adopted by many other compiler
> vendors) or "PACKED-DECIMAL" (part of the
> 1985 COBOL standard) data type. It is
> supported in PL/I as "FIXED DECIMAL". Besides
> the IBM System/360 and later compatible
> mainframes, packed BCD is implemented
> in the native instruction set of the
> original VAX processors from Digital
> Equipment Corporation and some models
> of the SDS Sigma series mainframes, and
> is the native format for the Burroughs
> Corporation Medium Systems line of
> mainframes (descended from the 1950s
> Electrodata 200 series).

Note that there is a difference between supporting
BCD format in memory and having the CPU support it.

Systems supporting BCD format in memory can process
them in 3 different ways:
1) BCD instructions in the ISA implemented in actual
    silicium
2) BCD instructions in the ISA implemented in
    micro-code
3) non-BCD instructions

All will support COBOL COMP-3 fine.

#1 will be fastest, so if COBOL COMP-3 is a huge
part of the actual workload for a given computer
architecture then it makes sense.

Arne

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Thread

Can Java compute 9^(9^9) ? bursejan@gmail.com - 2018-06-01 10:20 -0700
  Re: Can Java compute 9^(9^9) ? Eric Sosman <esosman@comcast-dot-net.invalid> - 2018-06-01 13:36 -0400
    Re: Can Java compute 9^(9^9) ? j4n bur53 <janburse@fastmail.fm> - 2018-06-01 20:20 +0200
      Re: Can Java compute 9^(9^9) ? bursejan@gmail.com - 2018-06-05 07:17 -0700
        Re: Can Java compute 9^(9^9) ? bursejan@gmail.com - 2018-06-05 07:29 -0700
          Re: Can Java compute 9^(9^9) ? bursejan@gmail.com - 2018-06-05 07:48 -0700
          Re: Can Java compute 9^(9^9) ? Eric Sosman <esosman@comcast-dot-net.invalid> - 2018-06-05 10:57 -0400
            Re: Can Java compute 9^(9^9) ? bursejan@gmail.com - 2018-06-05 09:32 -0700
              Re: Can Java compute 9^(9^9) ? Eric Sosman <esosman@comcast-dot-net.invalid> - 2018-06-05 13:58 -0400
                Re: Can Java compute 9^(9^9) ? bursejan@gmail.com - 2018-06-05 11:10 -0700
                Re: Can Java compute 9^(9^9) ? bursejan@gmail.com - 2018-06-05 11:21 -0700
                Re: Can Java compute 9^(9^9) ? Andreas Leitgeb <avl@logic.at> - 2018-06-06 08:50 +0000
                Re: Can Java compute 9^(9^9) ? bursejan@gmail.com - 2018-06-06 01:58 -0700
                Re: Can Java compute 9^(9^9) ? bursejan@gmail.com - 2018-06-06 02:01 -0700
                Re: Can Java compute 9^(9^9) ? bursejan@gmail.com - 2018-06-06 10:34 -0700
  Re: Can Java compute 9^(9^9) ? j4n bur53 <janburse@fastmail.fm> - 2018-06-09 21:06 +0200
    Re: Can Java compute 9^(9^9) ? v_borchert@despammed.com (Volker Borchert) - 2018-06-09 23:29 +0000
      Re: Can Java compute 9^(9^9) ? Martin Gregorie <martin@mydomain.invalid> - 2018-06-10 09:13 +0000
        Re: Can Java compute 9^(9^9) ? bursejan@gmail.com - 2018-06-10 02:31 -0700
          Re: Can Java compute 9^(9^9) ? Arne Vajhøj <arne@vajhoej.dk> - 2018-06-10 18:28 -0400
            Re: Can Java compute 9^(9^9) ? bursejan@gmail.com - 2018-06-10 15:48 -0700
              Re: Can Java compute 9^(9^9) ? bursejan@gmail.com - 2018-06-10 15:52 -0700
                Re: Can Java compute 9^(9^9) ? bursejan@gmail.com - 2018-06-10 15:58 -0700
              Re: Can Java compute 9^(9^9) ? Arne Vajhøj <arne@vajhoej.dk> - 2018-06-10 21:17 -0400
                Re: Can Java compute 9^(9^9) ? bursejan@gmail.com - 2018-06-11 13:20 -0700
                Re: Can Java compute 9^(9^9) ? bursejan@gmail.com - 2018-06-14 13:37 -0700

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