[Coco] Re: GCC: DFLOAT / DIRECT_PAGE

[Theodore A. Evans]

On 11/16/03, jdaggett at gate.net wrote:
> What is used in Color Basic is an adoption of IEEE Standard with an added
> "sub" byte to get 9 decimal digit precision. What it ends up with is 31
> bits in the mantissa. 9 decimal digit precision is standard calculator
> display! The RS Basic had to do this to use a 6th term in the Taylor
> Series to calculate the trancendetal functions with 9 digit precision. The
> sixth coefficient of the Taylor Series for the Sine function is one over
> eleven factorial. That is to small a number to be represented in standard
> IEEE single precision floating point.

I would hardly call it an adopition of th IEEE standard.  It has one
special vale 0, it does not have values for things like positive and
negative infinity and not a number which IEEE does.  The first bit of
the Mantissa is overlayed on the sign bit and cannot handle
denormalized numbers which IEEE floating point can.  Finally (going by
your code for unpacking IEEE doubles) IEEE is sign-exponent-mantissa
while Color BASIC is sign-mantissa-exponent.

-- 
You're my kind of man - bribable.
Theodore (Alex) Evans            | alxevans at concentric.net
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