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| "John W. Kennedy" <jwkenne@attglobal.net> wrote in message
news:KyjAf.3955$e9.3653@fe12.lga...
> robin wrote:
FORTRAN[color=darkred]
>
> You said -- it's quoted right above -- that the FORTRAN compiler for the
> 704 had to support double precision "in order to meet the standard",
> which is absurd, because the FORTRAN compiler for the 704 was the first
> FORTRAN compiler there ever was, and existed long before any standard.
And I replied that IBM set it.
>
> In one and the same posting, you said, "What's important is ... the
> number of mantissa bits," and then followed it up by indicating that the
> 360 did a good thing by increasing the exponent range at the expense of
> fraction bits. You can't have it both ways.
I didn't say that at all. Your "conclusions" are wrong.
What I did say was that the hardware considerations
related to the choice of hex, which reduced the number
of shifts during post-normalization from 23 to 5, and
for double precision from 55 to 13.
This arrangement (hex) gave a good range of exponent (roughly
10**-78 to 10**75) and a reasonable number of bits for the
mantissa.
>
> Actually, I didn't raise the issue of logarithms; Glen did. However, he
> was right; the use of "mantissa" to mean "fraction component of a
> floating-point number", though widespread, is an abuse, like using "k"
> to mean 1024.
YOU raised the issue of the word "mantissa" saying
that I didn't know what it meant, and implying that
I was using it wrongly, which I wasn't.
Whereas all along it was YOU who didnt know
what "mantissa" meant.
> I have already indicated how you contradicted yourself.
No you didn't because I didn't contradict myself.
>
> The actual format of a 704 floating-point number was:
>
> S (it was called S rather than zero): sign
> 1-8: excess-128 exponent
> 9-35: fraction.
Good, I'm glad that you funally worked it out.
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