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From: dick@ucsfccb..ucsf.edu (Dick Karpinski)
Newsgroups: comp.arch
Subject: Re: IEEE p854
Summary: 854 permits other sizes and decimal
Message-ID: <2194@ucsfcca.ucsf.edu>
Date: 10 Jul 89 21:03:08 GMT
References: <12194@polyslo.CalPoly.EDU>
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Reply-To: dick@ucsfccb.UUCP (Dick Karpinski)
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In article <12194@polyslo.CalPoly.EDU> mdeale@algol.acs.calpoly.edu (Myron Deale) writes:
>   IEEE 754 is the floating point standard for binary radix. Is p854
>intended for "arbitrary" radix?  or higher-powers-of-two radix?
>
>   In Cody and Waite's "... Elementary Functions" it is noted that radices
>higher than two are more subject to wobbling precision. In this light, what
>is the purpose of p854?

The committee was quite clear that their purpose was to extend the
benefits of a carefully thought out set of precision and exception
rules to other formats of binary floating-point (and to decimal
floating-point) arithmetic.  Specific sizes of exponent and 
significand in 754 give way to formulas relating the two parts of
a floating-point number.  Other radices were considered but there
was no support for base 8 or 16 since they are inferior to base 2
and lose the hidden bit trick.  Base 10 is inferior to base 2 but
has the distinct advantage that human readable representations do
not suffer any conversion roundoff on the way in and out.

Dick

Dick Karpinski  Manager of Minicomputer Services, UCSF Computer Center
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